Woe be the artist who doesn’t dot the i’s and cross the t’s. Who would expect to have that song become a YouTube sensation, or that illustration to end on on the cover of a magazine? FaceBook and Google+, etc. may weasel in on your rights too, if you post things on there. After the success, what do you have if you haven’t covered your ass?
And did you co-create a work? Do you have a collaboration agreement with everyone else? If you have a project that becomes successful, © and ownership issues may become messy.
Then again, there is also Creative Commons, which Flickr.com allows for content sharing. I protect my content under ©©. This allows creative re-use, but not to make money from re-use. You can scroll to the bottom of this page and read all about it. Try to make money off of my content, and >:)
A funny video on © your music:
This is not legal advice btw. Need that? Ask a lawyer!