I think the answer to that is what do MOST people use their camera phones for? Twitter, Facebook and sending to other phones. There will absolutely be people responding to this thread who will say that they use their camera phones for a multi national photography empire (because there's always SOMEONE who needs to argue every point made by anyone in every thread across the entire internet), but honestly, most people just want the highest MP simply because it's the most and therefore must be the best. Most users would be perfectly fine with 5mp. Heck, 2mp, let's be honest, would be more than enough for what people generally use their camera phones for. I like having my 8mp phone at my side at all times, but I honestly have yet to use a single picture for something other than facebook, twitter, sending to another phone or emailing them to someone, and most everyone else is in the same boat quite honestly.
Edit: Here's an interesting read from last year: http://www.adorama.com/alc/blogarticle/12858