Mid market is where the best value is. Give someone with promise a shot and mentor them and you'll end up with a great employee. The guy that works at Facebook, used to work for google, went to Stanford--might they be more likely to jump ship as soon as there's a new game in town?

I guess it depends on what you're going for, but I don't think the "best and brightest" mantra is all its cracked up to be. People can become better and brighter with the right guidance--only hiring the best and brightest and considering it an all or nothing proposition is lazy.

Edit: to be fair, as has been pointed out, there are engineers that are literally 1000x more productive, and they don't cost 1000x as much. That rare bird truly is best and brightest and is worth every penny. Trouble is, it's really tough to tell, and I don't know that the traits to look for are necessarily correlated with credentials typically attributed to "best and brightest". That is, those people don't all work at Facebook et al