WordPress.com has grown into one of the most amazing cloud architectures in the world. This has enabled blogs hosted here to have features unavailable on self-hosted WordPress installs. This makes us sad, since here at WordPress.com we want every WordPress install everywhere to be amazing.
With Jetpack, a new plugin from Automattic, people not on WordPress.com can now access features that depend on WordPress.com. Jetpack also provides convenience features that don’t use the cloud, but are now easier to install, or were unavailable as plugins before.