From W3C Wiki

For any computer program that offers to record my knowledge, integrity is job one. No other feature matters if, after 20 minutes of editing, it crashes and throws away my work.

I was once madly typing into a psion PDA and I dropped it and the batteries fell out. I thought surely I had lost my work. But when I picked it up and put the batteries back in, there was my text. Every last character. I'll take flash memory over RAM any day!

Emacs knows that integrity is job one. Its auto-save mechanism is very robust.

Evolution knows this. (mozilla thunderbird, alas, does not, yet).

OS X Mail knows this.

The danger hiptop/t-mobile sidekick knows this.

With these raves about SessionSaver, perhaps firefox knows this too.