Your friend probably fell into the excluded middle. The people who get to the Big Three are the really bad singers, or the jokers, who make for good TV, and the people who are really outstanding and likely to get sent to the next round. Unfortunately, your friend must have been deemed good, but not quite good enough.
Tell him not to give up, but to keep practicing and try again next year. Unless he doesn’t want to, of course; you said “yet”, which implies that he’s auditioned more than once.
Rilchiam, yea, he’s in the excluded middle.
He has tried twice for American Idol, but he competes in the local Louisiana Idols, and have won at least one of those.
You know, maybe next time I’ll tell him to do really bad for the preliminaries, and see if that way he gets to the judges… 
I know you’re kidding, but don’t. They’ve closed that loophole.
So you have to be singing as bad as you did the first time?
BTW, I had never seen Keith’s audition… that look in his eyes when he’s singing is scary!!
Yes. If they know you can do better, then they feel that their having been played trumps your cleverness. From what I understand, this stems from Scooter Girl, who sang badly in the prelims, then busted out with a Hollywood-worthy voice (but still brought her schtick) in the last round. They’re not about to let that happen again.