Celebrities and big brands already have the audience and distribution network to spread the word about their campaign, so it would seem that advantages of discovery through the Kickstarter community would be comparatively minimal compared to the fees, branding disadvantages, and loss of ability to re-engage those fans and backers post-campaign.

I've backed quite a few projects on Kickstarter, and most of the time I've heard about them through press or because people I know backed them (not by browsing through the listings on KS). I'd imagine that the vast majority of people who ended up backing Kristen Bell or Zach Braff discovered them similarly. Projects like Pebble, Ouya, and Double Fine experience the same effect.

The "hosted on wordpress.com" approach would take care of the tech stability/overhead while still giving those interested in more control a way to self-host. Look at guys like Louis CK, who've been able to do millions of dollars in sales through their site - a Crowdhoster type option seems much more attractive.