Open Authorization (OAuth), the authorization standard centered around the granting of permissions and the exchange of access tokens, has slowly gained more widespread use as a result of its adoption as an API authorization system for large web services (Google, Facebook, and Twitter all embrace some version of OAuth). Although OAuth version 2.0 probably won’t look much different from 1.0a to end users (if they even notice), most improvements seem to be aligned with the needs of a rapidly-expanding apps market. This is not a bad thing. When implemented correctly, OAuth can certainly improve security. Naturally, there would be an interest in simplifying things for both users and developers.
For comparison, OAuth 1.0a contains 2 main flows:
3-Legged: A complex dance by which an application (SuperApp) asks a server (Twitter) if it can act on your behalf (post some stuff).
2-Legged: A slightly-less-complex dance by which you already gave the application permission to post some stuff, and so it does it whenever it wants.
Both of these flows rely upon the security provided by the message signatures to avoid sharing the important secrets. And if OAuth 2.0 doesn’t provide an option for message-signing, there will always be some applications where OAuth 1.0a has a logistical advantage (especially considering the TLS requirement).
Sure, v2.0 might define some useful flows for specific things, and help improve HTTPS adoption, but OAuth 1.0a is a bit more well-rounded overall.