This is some thing strange when i observed Twittad . Twittad is a Advertising Agency where User over Twitter sells an Advertising space on his twitter profile page. and Advertiser buys an advertising space for whatever amount. Idea is not really bad. Social Site like Twitter allowing this is really great !! Twittad is working on excellent platform Plenty of users are over Twitter, so by few days Twittad will grow like Adbrite.
Just have look at following image( May be you need click on image for clear view !!)
In footer of above image you can found contextual ads by Google. If a company can’t bring some advertiser to there own site how could they get Advertisers for the Publisher ( Twitter Users) ??
My good luck To Twittad !!