Sure, stealing is wrong and I agree that if you start with someone else's creation, you should give them credit, however...You all realize there's no actual harm involved here right? Even if the "theft" was intentional, you aren't being cheated out of royalties or fame or anything, it's just your feelings that get hurt. So instead think of it as flattery that someone thought what you made was so cool they were inspired to use/repost it (changed or not). Isn't it possible that they saw your original and recreated it on their own? I've seen a bunch of sims in the gallery that look nearly exactly like my own. I myself take one of my own sims and maybe just tweak a couple things when starting a new game. Besides, I think you have the option to comment on creations in the gallery so if you do see your creation without credit among the bazillion creations out there, simply put a comment directing people to your original, just be nice about it in case you're mistaken.
