That's a common misconception. Fortunately I wrote https://blog.mozilla.org/nnethercote/2012/08/29/debunking-a-misconception-about-firefox-releases/ earlier today just for you.

I'm pretty sure there's a "ignore the warning just this time" option now.

Extension compatibility hasn't been a problem since Firefox 10; the max version is now automatically bumped. Furthermore, Firefox 4, 5, and 6 were kind of sucky releases, esp. in terms of memory consumption. Firefox 15 is a much better browser. UI changes since 5 have been minimal. It's also not full of security holes the way older versions now are. You should try it.

In practice we've found extremely few problems with "forcefully ripping" the memory away. In comparison, *many* add-ons no longer leak as a result. The cost:benefit ratio is massively favourable.

There's an option to turn it off. This is Firefox, which always has options for that sort of thing, unlike some other browsers.

Try it. Check out the user feedback near the bottom of https://blog.mozilla.org/nnethercote/2012/07/19/firefox-15-plugs-the-add-on-leaks/ -- people have experienced greatly reduced memory consumption, faster painting and scrolling, and fewer pauses.

The real problem is page faults. People don't notice how much memory a program uses until/unless it starts causing page faults. Some other observations and responses to this thread.

• One reason that browsers are using more memory over time is that browers are way more capable than they used to be. HTML5, web apps and all that.

• People say "I have N tabs open, Firefox is using M MB of memory". Often followed by "that seems outrageous" or "that seems reasonable". Without saying what those tabs have in them, it's pretty much useless.

• Firefox's memory usage has varied over the years. FF2 was terrible, and contributed heavily to the bad reputation. FF3, FF3.5 and FF3.6 were much better. FF4 is worse than FF3.6; FF5 will be better (it already is). Subsequent Firefoxes will hopefully be better again.

This is a known problem, due to some changes in FF4 regarding the discarding of decompressed images. See https://bugzilla.mozilla.org/show_bug.cgi?id=660577

It's global memory usage at the moment. I'm working on https://bugzilla.mozilla.org/show_bug.cgi?id=661474 which will give JS memory usage per "compartment", which roughly means "per domain". So if a page at foo.com has a Twitter feed and some Google Analytics stuff, there'll be three compartments, one for foo.com, one for twitter.com, and one for google-analytics.com. It's not quite per-tab, but in that direction. about:memory is evolving, keep an eye on it.

No: all general purpose tools can be used harmfully. A hammer can drive in nails or stave in someone's head. But some tools are clearly designed with harmful intent in mind. There's a world of difference.