It really isn't necessary to use something like Thai Friendly for trying to find lbs in Thailand - with dedicated lb bars and areas where they frequent, it's almost like shooting fish in a barrel. Quite different than in the Philippines, where the scene is more haphazard, and using dating sites to establish contact is the best strategy.
As for multiple profiles - it could be they are trying to attract more replies, or some may be "fake" copying a popular lb member's information to get some interest.
As for being angry with liars, cheaters, etc - wouldn't you be? It's also a waste of their time to chat with someone who is fantasizing about them on the internet with no intention of visiting them in Thailand, so that is why they want contact with someone local.
Is it a waste of your time? Not always as it is possible to meet some nice non pay for play lbs this way, or avoid a bar fine as some board members prefer that strategy.
As mentioned, I don't think it's necessary for a place like Thailand, but you're the best judge if it is a waste of your time or not. I am presuming you've read the advice for newbies on the forum (if not it's a good idea), and check out the bar and trip report sections.