Use cases for OAuth - what are your ideas?

I want to put a question about what ideas do you have regarding Open Authentication (oauth) and what are your use cases of that simple and genius protocol.

One use case is the Facebook scenario, where user data is accessed if the user authorize this access.

Another interesting use case that I'm thinking about is a payment API for Mobile Operators, because they have a way to charge their users' phone bill.

For example, if there is a mobile operator that has made a payment API (PROVIDER) that can charge users (simple charge operation with some amount) and this API is protected by oauth flow, and if I have a store that sells books (CONSUMER), I can tell my customers - buy the book and it will be charged on your mobile operator mo开发者_如何学Gonthly bill. And then if the user wants to use that option and purchase a book, she is redirected to the operator to authorize the payment (the request token), and I receive a response with access token that enables me to call the charge function for that customer. This can enable small businesses to use another payment option that is very spreaded, because not everybody has a credit card in the poorly developed countries, but a lot of people have mobile phones even in poor countries.

What are other scenarios where you would use OAuth?

Aside from Facebook, Google and Twitter are probably the most famous scenarious for using OAuth. Here is an impressive list of sites supporting OAuth:

• wiki.oauth.net/w/page/12238551/ServiceProviders