Even if the software is paid I would still prefer to get the source code in addition the binary when I purchase it. Because of this bias I'm willing to put up with the slight inconveniences of using free alternatives.
Another one is that I do a fair bit of photography and have been known to sell a picture or two from time to time. I use Aperature and Photoshop a lot. I have not found an OSS app with the same capabilities as either of these apps to support .RAW formats, elegant workflows, manage extremely large image caches (thousands of 13MP images and derivatives, etc.). The Gimp is powerful, but it is cumbersome (and I've spent many hours attempting to learn it), and seems (to me) to lag Photoshop by quite a bit. Also it is much harder to build on the work of others (part of the OSS spirit) with The Gimp because while many custom brushes, plugins and tutorials exist for Photoshop, they are fewer and farther between for The Gimp.
We are not looking for as many people using GNU/Linux as possible (althought that's sure much better than people using nothing but proprietary software). We are looking for many people supporting free software. So, having tons of users who don't contribute or care about free software doesn't make me happy. I'm not saying we should drop usability, it's important, it's nice, but we shouldn't confuse lack of proprietary application with usability, that's all.
Sometimes the end justifies the means. I'm sure that many of the Firefox converts didn't switch because of their love of free software. But it forces web developers to think about standards and not limit their web pages to Internet Explorer. So more users benefit you directly.
This essay explains a lot of my point of view towards software: http://www.gnu.org/philosophy/shouldbefree.html
I think finding what work best for me is just too selfish, I rather find what I think is best for everyone. Also, I realise that, althought proprietary software may be the best thing for me in the short-term, in the long run, free software will be much better for me. It will give me more freedom.
Now, I was hoping to have a serious discussion, but you call me a fanboy (althought for some reason people are downmodding me like crazy). Are you want to troll me?
I care about the consequences of my actions as well (or at least some actions, I am not to be held responsible when beer is involved), but free software != the absolute answer for everything. Do you not believe that everyone deserves to be paid for their work? Paying for software creates a cash flow for the company, which can be used to fund development, maintenance and enhancements. Some companies use that cash flow (IMO) in better ways than others, and that factors in to how I make my choices.
Free software doesn't mean you can't charge for them, it only means that the user of the software trully owns it, as opposed to simple having the right to use it.
Where I live it's very common to see companies that will write management software for other companies and sell it to them. I don't see any reason why they couldn't be selling free software, it would be very benefitial for the client because he would be able to even maintain the software if they want to. Or they can even contract a different company for maintaining the software. You give your client a lot of freedom this way.
If you release your software under a free software license, users are not only free to look at the source and modify it, they are free to redistribute it to others who have not paid for it.
If you can find a way to make free software work for you in a way that still allows you to earn a good living developing your software (such as by providing services), then more power to you. But for-profit software companies are not producing non-free software simply through myopia and ignorance.
Let's say a company wants to outsource the development of some software they need. They go ahead and contract your company. You develop it and sell it to them for a certain price. Even if the license is free it's not very likely that they will redistribute it for other companies, and even if they do, it probably won't fit their needs just right. OTOH, they will be able to call other companies (other than yours) to maintain your software. So they have that extra freedom. And it doesn't really hurt business because, if you do a better job maintaining your software than other people, chances are your client won't switch.
There's also the case of the end desktop user. That's probably harder territory for earning money with free software. But I've never seen some company selling their software but giving the user a package with the GPL-licensed code. Sure, after a while there would be lots of other non-official sites to download the program from, but doesn't that already happen with all the proprietary softwares nowadays? And it's not like anti-piracy laws are doing any good against it. This way people may do their own derivative work, for which they might even charge just like you. Now you'll have competition, so things get more interesting and you have to make better stuff. Why can't that work?
You can still charge for constant patches you deliver (though they are all GPL'd). If it's an online game, you might charge for your server, and so on. A big part of software nowadays seem to be services, anyway.
Say google opens the source for their search engine. Why would you turn to a different site other than google.com? It would make great research environment, nonetheless. Even google could gain from it.
So, what I'm saying is that I don't see a reason why people can't earn money while keeping their software free. Even though things might get a little different from what they are today. That's good, though, because today is far from perfect. And I think free software is a move in the right direction.
If someone openly pirates your proprietary software, you have legal recourse. If someone openly redistributes your open source software, they are acting within their rights to do so.
In fact, a third party repackager of RHEL even has the option of charging to provide service, at a discount from Red Hat's price, and they can do this perfectly legally.
Short version of the economics: if you can charge for services, you can make money on open source, but only client by client -- you don't become more efficient the more services you sell, unlike with products (especially low-marginal-cost products like software). You have to add employees for each new hour of services you provide. So if you have a potentially popular product, all other things being equal, you have a higher potential for growth if you sell the product rather than the service.
Of course, all other things aren't equal, which is why the desktop software market has been in decline since its heyday in the 90s. Because the marginal cost of each unit you ship is so low, when there's plenty of competition, you tend to see a race to the bottom on price (unless you can convince people to buy your product because it is the standard, as Microsoft has done).
Many enterprise markets are small enough niches that (1) there are a limited number of competitors, and (2) if you give away your product, you may not easily be able to make up the revenue in any other way. On the other hand, if you have technically savvy clients, you may find it worth your while to offer them your source under a non-redistributable license. They still have to buy your product from you, but they can debug against the source, integration test, etc. This isn't free software (obviously), but it may be a happy medium for both you and your clients.
And yes, when the option of selling (or monetizing in some other way) access to your server presents itself, that can be far more profitable than selling a client-side product. That's why World of Warcraft is ridiculously profitable, and it's why Google makes so much money. But it seems clear that this works better for some markets than others.
I say all of this as someone who believes in free software wherever it is practical, but also as someone who makes a living writing software and wants to continue to do so.
And, as Eric Raymond argued over a decade ago, for something like an operating system that is used by large numbers of people, there will be no shortage of free labor to produce an open source product. But people will probably only work on software for managing a multinational mineral extraction business if you pay them. So open source is a great idea for many, many things, but probably not for everything.
Who cares if the software is free or paid? OSS or proprietary? Find what works best for YOU, and go with it. Note that the best answer is likely to be very different person to person.
Fanboys of any denomination are all equally annoying and blind.