'What Part of "No" Don't You Understand? Explaining Copyright Law to Publishers' is a noble and patient attempt to explain licensing to would-be rights-grabbers, by Rohn Engh. If you've ever been lost for words to argue your case, it's well worth committing his piece to memory:

For freelance photographers used to licensing their photos, it's always a shock to come across an editorial stock photography buyer who thinks that payment for a photo covers both present and future use. Unless a work-for-hire agreement is arranged in writing between the photo buyer and the photographer, payment for the use of a photo is for one-time rights only.

...continues at the Blackstar Rising blog