ah i see what you mean mark0, from the about page:
The purpose of forumposters.org is to match forum owners with quality forum posters who want to be paid for posting on forums. Paid forum posting is useful for creating and maintaining a quality forum that attracts users who you want to stay and contribute to your forum as well. Without hiring at least a few forum posters, it can be difficult host a forum that is of any repute and value to advertisers. Forumposters.org does not charge forum posters or forum owners for the service that it provides. Forumposters.org is a free website for matching forum posters with forum owners.
This is interesting but from reading the forum it still troubles me.
I suppose this could be acceptable if
1. You made clear up front to everyone that the people posting were being paid
2. You were paying them to add content of value to the forum or help others, answer questions, etc.
It seems very shady though, and i wouldn't go near such a forum with a 10 foot pole. It sure looks like the people using their service won't be telling their readers that the posters are paid which is not cool, to put it mildly.