Oh I totally agree! With sites like Tumblr out there it's impossible to stop it completely, unless I go to extreme measures and have my own site that only allows a select few in - which defeats the purpose of sharing art in the first place considering I don't think mine's good enough to ask people to pay to see it.

I still get that knee jerk reaction though when people recolour my stuff or just outright claim it's theirs. That's when I get annoyed and need to step in. Otherwise a simple redistribute is okay - except in this case when I had already asked for it to be removed and they did a sneaky and brought it back up.