I'm not looking for a job currently but my CV must be out there somewhere on the internet from the last time I was looking for work. And it's pretty clear quite a few recruiters just do a keyword search and send out emails without actually ever reading my CV. So I've had emails about C++ positions, which I haven't touched for almost 10 years, PHP jobs, which I'm familar with but wouldn't consider a strong point, testing jobs and even jobs in the US.
Maybe the 'throw enough shit at the wall and some of it will stick' technique works but I suspect it's not highly effective. I tend to remember the recruiters who actually bother to ring me up and actually listen to what I have to say and if I ever need to contact a recruiter again I'll go to them first, since they appear to care about placing people in the right job. The others are simply helping to confirm the bad reputation that recruiters have.