The reason why this happens to a lot of developers is because:

1) They have a LinkedIn or Stack Overflow account.

2) They have dealt with a recruiter before, either looking for work or from cold calls.

I've had the (mis)fortune of both. The only people that ever look at my LinkedIn profile are recruiters, so I regularly get emails about crappy jobs. Hell, it's not unusual for a recruiter to offer me the same-level job at the company I already work at, sometimes even by phone...

It'll happen, so I won't worry too much about it. It's largely a talent market out there, and if you've spent enough time at a company that gets hounded by recruiters or a recruiter finds an online profile of yours you'll be on a "list" too.