People are scamming everywhere.
This has always been happening since the start of the forum. It was why the trust system and default trust was introduced. Various members try to combat it using the feedback on the trust page. Really, though anyone dealing with another user on the forum should use escrow.
Theymos isn't doing anything about the tons and tons of issues.
He's started two discussion threads about the recent problems and asked the communities feedback which to me looks like he's trying to do something about the current situation.
Most of the problems that you have mentioned has been happening since you have been registered though, so I don't quite understand how you see anything different. These problems have existed for at least a year now.