Well I'd rather see those yellow stickers on cars, than those inane Garfield's that were popular a few years back, but go ahead and mock those people who support the troops(ala Kevin Tillman).
A sticker on a car is trivial support...makes the owner of that vehicle feel like he/she/it is doin' something...and yes, I wish I'd had thought of the idea, so I guess I'm jealous...