Firefox hasn't supported running multiple profiles simultaneously forever, though I understand that it's possible now. That's actually party oh what got me on chrome originally--I could have my school profile open at the same time as my goofing-off profile and pretend to be researching while I played flash games, yet not showing any of that in my history.
Firefox has supported running multiple profiles simultaneously since before Chrome ever existed - I used them. Chrome was first released in 2008, and here's an article about Firefox's multiple instances from 2007: http://turbulentsky.com/how-to-run-multiple-firefox-profiles....
