I've issued DMCA requests when I've spotted my stuff being copied and pasted before, and after much chasing, the offending pieces were removed. But it's very time consuming and annoying when they don't respond, and I can quite understand why you'd rather just let it go. For me, the experience has made me more careful what I put on here. If I can sell the story to a magazine, or I may be able to sell a reprint later, I'll try that instead. Because once something is all over the internet, a magazine won't touch it.