mcaloney

Of course, but if I let my friend use my computer to check gmail, he or she could go to Firefox -> Preferences -> Security -> Saved Passwords and see all of my passwords anyway. By letting somebody use my computer, I'm implicitly trusting them to not misuse anything they might find.

This episode of Skeptoid - http://skeptoid.com/episodes/4036 - discusses this very video and concludes that what we're actually seeing in the video is water vapour (since mercury vapour is much heavier than air, why is it rising in the video?).