Limping with AK is an OK play when doing it for the reasons Irexes said. Let me just add a few things that are absolutely paramount:
If you limp with AK and get raised, you're not folding. You should consider re-raising.
"Only ace-high" is not a correct way to assess a flop. This is a game with 7 cards and before they're all out, you're better off considering your hand in terms of
equity than in "
poker hands." This is pretty important and is one of those things a lot of people seem to struggle with.
So when we raise AK preflop, we do it because our equity is huge. We do it because people will call with
hands that we have dominated. We do it to build a pot for all those times that we do hit the flop.
What I'm trying to say is this: If you're going to give up the huge value that lies in raising AK preflop, you must have very good reasons for it.