I think that Dan Russell describes it so much better than I could ever hope to in his post Screaming users considered good.

When creating systems that are meant to be used by a large number of people, it is very easy to end up pushing one’s own agenda rather than working out what suits everybody else. I love reading what you think is right, wrong, broken or pointless in Bouldr - tell me what is bugging you or what you love, and I’ll see to it that Bouldr is built in the right direction.

Oh, and on a side note, this video of Dan Osman is insane!