I'm late to this discussion but felt I should post this information as I just read it on a newslink I get from ZDnet:

"My colleagues at Kaspersky Lab (see disclosure) have intercepted two new worms squirming through MySpace and Facebook, using social engineering lures to plant malware on Windows systems.

The worms propagate via the comments features on the two popular social networks, using video lures and fake Flash Player downloads to trick end users into installing malicious executables."

So, as with so many internet sites you need to be careful what you do.

The full article can be found here: http://blogs.zdnet.com/security/?p=1615&tag=nl.e550