The whole concept is flawed imo. You want a hat for TF2, because you map? I'm sure your chances of gaining a hat would be significantly more if you shut hammer down and started playing TF2 more often. People who want hats should play/idle in TF2, those of us who map because we enjoy it shouldn't be any more rewarded than those people who play TF2, and ultimately, decide valve's next move. Whether it be via custom maps made official, or whether it be good ideas emailed to them. We are still players for TF2, nothing more. Yeah we like to map for it, but so do the people who create maps like orange and lol2fortremake_100000. You are essentially rewarding "good mappers" and also those who keep on releasing, well, crap. Those people will still be here in the SDK carving spheres and going "loldoesntwork"
You'd essentially be rewarding this dude:
[ame="http://www.youtube.com/watch?v=xh9Kr2iO4XI"]YouTube - Making terrain in Hammer using carve tool[/ame]
Do you really want that on your head?