* Every app can access your address book, getting an instant social graph. The phone number in particular acts as a unique social identifier
* They can access the photo library and camera directly (and location), making sharing easy
* Push notifications mean you don't need people to keep checking your site (or open emails).
* Every app is just two taps away on the home screen, which makes switching services easier, and also drives a trend for focused, single-purpose apps over apps that do e...