Ensuring your app loads quickly over the network is definitely an optimization, but to call it a micro-optimization is wrong. Size on the wire for html5 apps (frequently loaded over mobile connections) is completely relevant.

Those in that situation should probably start by optimizing the whole "frequently loaded" part... by not frequently loading it. Then they would realize this shaving of a few hundred bytes here and there is, indeed, micro-optimization.

3g is virtually ubiquitous. And building an app having weird contingencies in mind (atrocious wifi connections, 5 billion people downloading simultaneously, downloading from outer space, etc.) is not good engineering. Unless you like spending time in development hell.

"Oh no, our application can't be simultaneously downloaded by 3 million martians because our client is too big." I'm being facetious, of course, but I think the point applies. Don't build stuff with weird contingencies in mind. The average user (of an HTML5 app) will not have to worry about processing power, bandwidth, or client size. As long as it's not like 20mb or something stupid.

It is well known that lower response times increase conversions and reduce abandonment on any website. There is absolutely no reason for a website to cross the 1-2mb threshold unless it's a huge web application, a game or image-based app, or is serving you hi-res photos.

And, obviously, websites are accessed from all kinds of connections. Not everyone has a generous 3G plan, and even the US doesn't rank that well in average broadband speeds.

One third of the US audience is not a "weird contingency"; it's basic awareness. Developing only for the highest of the high end is not good engineering. Get your head out of the cloud.

I'm reading your comment on an intermittent 2.5 g connection.

3G isn't nearly fast enough to make megabytes irrelevant.

And setting hard limits is the best way of ensuring that your bigger problems ARE elsewhere :)

Anything you don't have a limit for will become a problem. I don't care how fast computers are, or how much memory they have, or whether you have fibre-optic broadband. If you treat the resources in question like they're infinite, you'll find out the hard way that they most definitely are not. And that's so silly, when you can just set a reasonable limit that guarantees you won't have any problems, and then... not have any problems.

Realistic limits aren't so hard to stick to if they're there, and enforced, right from the start.