Everybody knows that the web is a more open platform than apps are. But when asked why, people focus on the app store and its gatekeeper, and overlook the crucial importance of discoverable links. Links enable any website to cast a vote, to say "this is important" and the ease of following links gives this vote power. So why don't apps have discoverable links like their website counterparts? An app developer has no incentive to build and expose links because no service takes advantage of those links.
This might all be about to change. Benedict Evans has some good thoughts on Airdrop, which is new in iOS7 and allows you to share content which has thus far been locked within apps. Airdrop is the first good incentive for app developers to create links, because links are a prerequisite for Airdrop support. If there is widespread adoption of Airdrop, half of the puzzle is complete. If something comes along that allows others to discover an app's links, a huge opportunity emerges to make sense of the links.
As a side note, any organization that thrives on links should do everything they can to encourage app developers to expose links, because as the world shifts increasingly to mobile apps their very survival might depend on it.