If someone clearly looks like someone capable of participating in closed beta test, and the people (GMs) who know / have heard that this someone would be a good betatester, then he will be asked. Being a "friend" or "close friend" to a GM through whatever means isn't a full guarantee for automatically getting in "important positions", but I don't decline the fact that it does help in choosing.
Someone who posts a topic and says: "Hey I'm a good betatester, pick me!" is rather unlikely to get any kinds of positive recognition, as obvious as it should be.