One of the powerful constructs of AngelList is social proof. It’s become an important part of the seed / early stage venture process as very early stage investors pile into companies that their friends, or people they respect, are investing in. AngelList does a nice job of exposing and promoting social proof during the fundraising process in a way that is both legal and non-offensive.
As with many things in life, the key lesson is to do your research.
Social Network faces a danger of herding behaviors. Only when everyone is doing his/her share of work can the network be of high quality and sustainability