The original Daily Paintworks group was established and had a good thing going long before they opened it up for general membership. Why would you expect them to completely give away any and all benefits of their founding status?
David has done an amazing job of building a fantastic, low-cost site that is searchable in mutiple ways. He further leveled the playing field by featuring and promoting everyone’s art in a variety of places: Facebook and auction “picks,” the weekly challenge, the monthly contest, the free gallery pages, the blog widgets, etc. I have watched a number of general (non-featured) members seemingly to do very well here. Your own efforts are always the most important component of any type of marketing. I think the price one can command is determined much more by skill, reputation/demand, and time in the saddle than by having “featured” status.
You knew the deal when you signed up, and if it doesn’t work for you, you can always quit. But I don’t see how posting a cranky complaint on their discussion board is going to further your cause. That seems remarkably impolitic!