You have a very good point in the last sentence of your last paragraph, (“Still I worry that as unconferences become more of a norm and widely used we will have issues with people who are quite full of themselves.”).
Perhaps we can solve that problem with an Ego Gallery, where people post complaints of people that promote themselves one too many times. (Maybe the Ego Gallery can be tripped by a specified number of different people voting on a someone, like votes from 10 different people).
Also, maybe the Twitter back channel can help alleviate this problem. The channel just needs to be prominently displayed.