I have Windows 7 and Mint Linux on my computer. I had changed the e-mail address I use to log into Facebook (and I did this on Windows). The next time I logged into Linux it had the updated e-mail address in the username field, as if it had previously been cached. Does Facebook use Ajax or something to automatically update the old e-mail address to the new one? Or does the Firefox on the Linux side somehow share stored form fields with the Windows side?
I noticed Amazon.com had remembered some stuff I added to my cart on the Windows side. Maybe it's session cookies?