Third-Party Free Sites... Undermining Authors Sales?

I just discovered a site where my book has made available for free downloads. Interestingly enough, I didn't sign up or authorize this. And it appears that there are many other books being made public for others to pick up free.

I understand if I set up my book to be available in a public library then I might gain readers but lose out on sales. That's my choosing. But to find it out there in some scab site for anyone to grab leaves me feeling cold. I don't expect to roll in cash with each book nor do I expect to top the charts, break records or fill the world with my particular brand of wisdom. I just have stories to tell and feel damned blessed that there are people out there who enjoy them. I am trying to make this my career and help support my family. Watching the book slip out for free undermines that respect of my new goal in life. It's a little hard to swallow, even with a stout cup of black coffee.

Not sure if this is a reportable issue or something I will have to learn to deal with as I put my work out on the internet. This may be just another hurdle other authors have dealt with and now it's my turn. Or maybe I should take it as a compliment that someone thought it was good enough to share with everyone.

Not sure which way to go. Guess I should look at it as an opportunity to gain and grow from it.