These days, theft of copyrighted work is becoming far more prevalent because people can copy and paste your work, and then stick Google ads in there. I don’t know if they can really make much money, but enough people are doing it to suggest they can.

I agree with the comments above, that on a personal site it shouldn’t usually be such a major concern, but then that does assume a few things that may not be the case. If you put a lot of hard work into something – and use your knowledge, skills and experience – then it shouldn’t be allowed to be stolen by others. The copyscape tool allows free checking of web pages.

I use Copyscape as well, which although limited, and in ways, very underdeveloped, it's the only one I can find. You can display copyright warning logos from them.

The first time I used it I found 2 major infringements, where entire pages of mine were ripped off and presented as their own work. One was full of Google ads. Most of the copyright theft I find is done by so-called web designers who are doing it without the site owner’s knowledge and when informed, the site owner is usually embarrassed and not best pleased with the thief.