If you're looking to hire a good programmer, think of what good means to you and what specific skills your project needs and write them down. Writing "rockstar programmer wanted" is a hint that you can't even do that (instead you're pushing hype-speak), which sets off alarm bells. Also, at the end of the offer you can write something like: if this sounds interesting to you but you don't exactly fit the bill, you can still apply, but also attach an explanation why you're interested and why we should be interested in you.
I've always been confused by the "rockstar" thing as well. I know what they're trying to say, but it seems like a strange metaphor. Rock stars are quintessentially style over substance. Sure many of them are competent musicians, some are even very good, but that's pretty incidental to their rockstardom. A rock stars main job is to look the part and sell the brand while others do the heavy lifting. That seems almost the opposite of what you'd want in a programmer. What you really want isn't the rockstar, but the virtuoso guitarist who is always kept slightly in the background but is the main reason why the rockstar sounds so good.
Who describes themselves as a "rockstar coder"? If you're young and realistic about it, you can't have enough experience to tell. Most good experienced programmers I know are modest people and would never describe themselves as "rockstars" and would never apply to such an offer.
This seems to be a way to get "arrogant coders" to apply...