Originally Posted by Profits of Doom

I think the only real way you are going to be able to keep people posting is to pay them a set fee per post. The advertising factor is nice but if for any reason they feel they aren't getting a good ROI on it, as far as time writing to actual jobs received, then the blog will fall to the wayside.

Maybe you can also offer them some traffic from one of your other sites if you have compatible projects...