The behavior of recruiters is puzzling to me. I've repeatedly been contacted by recruiters who want to talk to me about opportunities at X (where X has been Amazon, Google, and a few others). I've responded to these and then received no further contact from the recruiter. They go to the trouble of making a pitch to me and then disappear when their pitch is well-received. My only guess is that they're operating like a telemarketer, spamming the message out to some large number of people to ensure they get a few responses and ignoring any extras.
Just last week a Google recruiter contacted me and gave me a link to his calendar to schedule an appointment. I made the appointment and he no-showed. He later contacted me and said he'd spent the day at a conference he received a last-minute invite to attend. I'm just astounded that these folks treat people with such contempt, given that it reflects poorly on them and the business they're associated with.