Giving credit.

[Dazz]

My 2 cents, because my opinion may be kind of twisted.

I rip sprites because I enjoy it. I don't rip it to become well known, and sure, it helps people, so I'll distribute what I rip because people like it. But the joy of ripping from something is that with it I learn how certain things work in an artistic sense, ways of animation, even to some degree how a game implements its graphics.

For the most case, I find ripping easy. It's when it becomes hard that I'd like to have a bit of thought go my way, a nice "That was nice of him" sort of thing. For the most case, I'll stick a tag on saying "You can give me some credit IF YOU WANT" - That's the way I think it should be.
But even so - other people may want to become well recognised for the work that they put in to actually get the stuff for you. The exact same goes for any part of a business that uses someone else's research, or even a photo.
"I could have researched that" or "I could have taken that photo" results in serious penalties. Of course, this is sprite ripping, a touchy subject already, so those penalties will not be enforced here. We release sprite rips on public trust that we all have in that "they won't be total jerks".

Sure, you can go ahead and be a jerk - but don't expect a community of a few ten thousand strong to think positively about you in the future.