Normally I think folks who post complaints about Priceline just don't understand the Priceline proposition very well and come off half-baked... but I think redtop43 has a great point here. Any fee above the stated room price should be optional, or else the stated price is false and deceptive.
I certainly don't mind paying extra for valet parking if I want to use valet parking, or a wifi fee if wifi is not free and I want to use wifi. Being forced to pay a previously undisclosed "resort fee," though, whether you intend to do resorty things or not, should be a matter for the FTC.