I think it's fairly obvious from all of these stories about the Google recruiting process - being pestered fairly regular by different people who appear unaware or indifferent to your past experiences with Google, either as an employee/contractor/failed candidate - that the recruiters have some sort of quota system and need to keep feeding potential candidates into the interview process to meet their own metrics. Hence why a lot of times it seems like someone is being contacted out of the blue based upon an "online profile" that someone stumbled upon through desperate-seeming research.