Watch out with Digimarc, and other 'invisible' watermarking software. They will not deter copyright infingers. They only make it easier to find and prosecute. To deter such behaviour, you need to have something that is obvious. And which would you prefer: To not have something taken at all, or to be in a stronger position for taking them to court? Digimarc is fantastic if the second is what you are looking for. I'm just not sure that that is what most independant artists are looking for.