My idea is to implement a reputation score starting at 0 for newly created accounts. They can post anywhere but in the Markeplace section and can't send PMs. Whenever a member finds a post worthwhile, they can click on the button near the post to give some reputation points to its author. While a member has a reputation score < n, the Marketplace section and PMs are off limits to him/her.
In order to avoid abuse, newly created accounts have a reputation power (the number of rep points left on each click) of 0, so that scammers can't create multiple accounts with the sole purpose of giving each other rep points.
Also, each member category may have a different reputation power: x for Jr Members, y for Members, z for Sr Members, etc.
This way only people with a minimum threshold of quality contribution to the forum are entitled to the Markeplace section and PMs = 95% of scam attempts instantly gone.
good point this one idea can help to avoid many scams for sure.
Reg.