I've been working almost exclusively on apps that run in web pages for the last couple of years. Because of this I'm pretty sure I see a way that browsers could be smarter about loading these apps.
Consider an app that's launched by a bookmarklet.
The user is likely to accumulate more than one tab running this app if they use it a lot.
Each of these tabs has a copy of the app's data in memory. It's possible to keep them in synch using localStorage. It's pretty cool the way that works. It's not hard.
But it would be even better if there's a way to signal to the browser to re-use tabs for this app. So if there's already a tab that contains this page, just bring it to the front and reload it.
It would be nicer for the user, and perhaps a little more reliable.