Agree, Pekka. There is still a lot that needs to be developed and understood. The values of the tokens will all depend upon supply and demand just as with any other currency or commodity, and paying taxes on income won't be any different than it is now, as far as I know. This will all need to be sorted out, though, and clarified. Some are developing best practices and other regulations are sure to follow. I'm not sure what you mean about "receipts"?
These are the major players so far:
Photochain
Wemark
IPStock
KodakOne
Copytrack
Yes, I've turned off right click capabilities for my site deliberately. I realize that is not ideal but since there are referral images on my site, I don't want anyone to be able to access them on my side...