My DH response to this was "Straight men already wear heels, they're called cowboy boots".
I'm all for live & let live, but my take is that most men can't pull off ladies heels. There are such strong associations between high footwear and femininity, it is hard to make that mental cross over gender lines. We have strong gender taboos on masculine/feminine that we are raised with, heels are just one example - and so, for most of us, it simply looks 'wrong'. Like anything else, there will be some men who can pull off a whole 'look', but most average men won't be interested or able to pull it off.
Though I do have to agree with a previous post that Prince always rocked the look - androgyny seems to help a guy 'work it'. And did anyone else notice that Ricky on last season's Project Runway seemed totally comfortable when he donned a pair of heels during the weight-loss challenge? I love my heels, but I think that kid could totally smoke me in a heels race.