If you don't have a product, the benefits are more along the lines of finding your voice, learning what resonates with the people you care about, and getting comfortable putting content out where people will see it.
I mentioned the numbers in the sense that I used to think traffic and on-site behaviour was a magical thing that "happened". It was more about having that "aha moment" of how it all works than about doing anything particularly profitable.
Given all that, I think new & future founders would do well to try blogging for a while, reaching out to whoever your future customers would be. It lays a bunch of strong foundational skills that are tough to internalize through reading case studies.
I know this sounds like a "you can too" commercial but I actually did. I posted it on text-link-ads.com and sold a load of text-link ads (i.e. google juice) at the bottom of the page. From that more marketers discovered me and then bought ads direct on a year upfront basis.
The amount paid ranged from about $20/month (of which I'd see half) with TLA to $100/month (I kid you not) for direct sales. It's whittled down to nothing now but it worked out about $10k or so of revenue over the two or three years after I finished blogging which wasn't too shabby.
Obviously Google could wake up one day and kill you for it but since I didn't have any audience I also wasn't bothered by that.
(Great button btw Rob :)
And yes, they've also realized that all those subscribers are good for more than just ads, so they're upselling them books and videos and seminars and whatever else.
Certain blog posts of mine have made several hundred dollars. I refuse to believe that I'm the only one.
Edit: I'm talking about blog posts written in the last five or six months, just to clarify.
If you are a starter at HN, then do not get misguided by the quote above. If you are aiming for using blog writing as SEO for product marketing and reaching out to new customers then it is good effort. But if you are looking to get eyeballs for adv revenue then stop right there. There are better things you can do with your time.