When I taught, my students used to ask me about the dangers of people copying work. They thought that if a story was published online, it would be really easy for someone to steal it and send it to some other place to be published. The thought being the Internet is so huge no one would notice.
I would always respond to that question by telling them not to worry about it. Not because it's never happened, maybe it has, but I told them not to worry about it because if they are strong writers, they can brush that theft off and write something ten times better. I don't know, if you're rich you can sue or something. But if you're us, it's more of an emotional bruise than a financial one.
But, here's the thing, have you ever been writing something and said to yourself, "This is familiar." And dug through books, or your own damn memory, and realized it's familiar because someone else wrote it?
Or have you ever read something by someone else and thought, "I already wrote that," and dug through your shit and found that yes, you wrote it and read it out loud and now something similar is in print with someone else's name attached. And maybe that person didn't consciously "steal" anything. Maybe, while they were writing it, they thought, "this is familiar," but they continued on writing.
When that happens, it's hard to take your own damn advice. It's hard to brush it off. Seems the remedy is to sit down and bitch about it on a blog and then drink some coca cola and write some new shit that's ten times better than the old shit.