Did you post a link on Twitter, Facebook or maybe even Plurk? And then someone who "follows" you or is your "friend" went on maybe a few days later and posted the same link without crediting you as a source?

Well, maybe you weren't the source. Your social media followers and friends have most likely loads of going on and unfortunately they won't be able to see all of your nifty links and other posts. It happens.

Of course it's always nice and polite to credit the source. But it's not mandatory and you cannot know you were the actual source. Perhaps they happened to follow that same blog you did or stumbled upon the content somewhere else. Unless it's actually your blog post, your original tweet, your something, don't think it's somehow yours.

You'll be likely to present yourself as a total dick if you go and tell the person you just whatevered this the other day. Don't be possessive about it. Just move on.