I am not a member of that site but I've read it periodically to see what the criticisms are all about. It's possible that I'm simply not familiar with the members and those who are active on the site know who they are dealing with. But one problem I have is that members frequently post photos of items and they'd like opinions on its authenticity. Members reply with brief comments like 'Good', 'Crap', etc., etc. The problem I have is that it seems that the people who reply may or may not know what they're talking about but it's just assumed that the responses are accurate and valid. There is no attempt at discerning whether or not the 'authenticators' are in a position to make a value judgment or whether they may have ulterior motives in passing the signature they are seeing that is being questioned. Beginning or less experienced collectors seem to be assuming that all of the people on that site are knowledgeable, trustworthy and legitimate and this appears to me to be wrong in multiple instances.
Case in point: Someone posted a signature of Stephen King in a copy of Lisey's Story. Three people replied and all of them called it 'good'. Personally, I think it's a laughable forgery and if the OP bases his decision to purchase the book based on these three opinions, he's going to get taken. Does anyone here who knows King's signature think that this one is authentic?