http://www.bikeforums.net/showthread.php?t=394724

This thread may help, while it's mostly focused on UK commuters there are a number of US commuters subscribed to the youtube channels. The helmet cameras were successfully used by a number of people as evidence gathering tools.

However, there's also been a few other responses, from both police and the guilty parties, including "it may be illegal" (it's not), "we can't use that" (you can, actually), and so on. It really depends on how hard you're pushing and if you've got all your bases covered.