The QuickMatch system on OkCupid has the exact same fatal flaw.

It's a similar sort of thing. If you rate someone highly, they are notified that "somebody" rated them highly, but they don't know who did it. If they rate you highly in turn, then you're both notified. What ends up happening is a lot of people rate everybody highly so that they find out who rated them highly, ultimately defeating the purpose of the system.