Stuff

Amazingly, this problem is still there after at least a year I think. There have been a bunch of fixes published, but the one that worked best for me is this one:

How To Stop The Firefox Memory Leak
1. Open Firefox and go to the Address Bar. Type in about:config and then press Enter.
2. Right Click in the page and select New -> Boolean.
3. In the box that pops up enter config.trim_on_minimize. Press Enter.
4. Now select True and then press Enter.
5. Restart Firefox.

Now every time you minimize Firefox, the memory will be cleaned up. I really had to get in the habit of doing this, the app was regularly taking up all the memory on my machine.