Paying for posts is inappropriate, and the FTC agrees. Link-building contests -- for example, John Chow's "review my blog and possibly win a MiniTV USB" -- also rubs me the wrong way. (I have no qualms with link games like hat-bait, the z-list, and blog tag.)
Call me old fashioned, but I agree with Seth Godin's purple cow thesis: the right way to capture attention, mindshare, ink, pixels, word-of-mouth, buzz, links, and general PR love is by having a remarkable product or service. A hundred times harder than writing checks or running games or linking tricks, yes. But, at day's end, this is really the only way.