What's with the challenges...

Okay,

First off, I know I am going to sound like a arrogant ass for bringing this up so I'll apologize in advance...

What is the deal with the challenges? I recently participated in two challenges where I did well (3rd place). The first place winners were great photos, but the 2nd place winners were pretty lackluster (understatement) IMHO...I see a big disconnect between those shots and my placement behind them.

Are people "buying" votes? Why the disconnect?

Please note that I am not saying the 2nd place winners were terrible photos, but even when I try to remove my bias towards my own work I am not seeing it...

For your reference, the challenges I am referring to are:

Military Jet Fighters
http://www.dpreview.com/challenges/Challenge.aspx?ID=7277

and

Benz (as in Mercedes Benz)
http://www.dpreview.com/challenges/Challenge.aspx?ID=6941