With my photographs, it doesn't bother me too much - because I'm not a good photographer, just a point and shoot type with the basic concept of getting things you want to shoot in the frame and things you dont want out of the frame and trying to get sun in the right direction. I take them to share them, and would only get miffed if attribution wasn't given. If I really were to take something worth taking I'd probably look into a better licence and think twice about sharing through twitter-type hosting sites.
However I've had other images hijacked by the BBC in the past (well before days of creative commons licences, twitter, flickr or anything) and resorted to a bit of letter writing without really getting anywhere with BBC legal dept.
Anthing I've created that I think is any good and want to share is stored on deviant art and only versions with lower resolutions watermarks etc.
A lot of stuff has been put onto wikimedia with PD or CC rights. Some of it has ended up in some limited run books and it's always nice to get the email asking if they can use it.