I don't want to host every WordPress blog in the world -- too much trouble. :) Also not how the internet should work. This gives you the best of decentralized and centralized. Many of the third-party hosts are doing crazy-nice stuff already with scaling and failover, they just don't market it in a Heroku-manner because their standard pricing works so well. (The launch partners for Jetpack have close to 2B in revenue collectively.)