I thought the way they used the "Meet the Team" teasers was really clever:

"Each content update started with a teaser trailer that hinted at several possible new items or features, and Valve developers would monitor the community reaction in the forums to determine which aspects caught the players' attention."

I had seen these, and had always thought Valve already planned out what was going to be included. Like magicians, they set themselves up for victory - no matter what the player ends up wanting.