The real question is : are the developers or the providers that actually struggle with oauth?
If providers followed well standards, developers would not struggle to implement all these current oauth versions.
Providers suffered from the different versions, and the 2 years it took to come up with a final OAuth 2.0 version.
e.g. they were trying to their best when they copied Facebook's implementation, they thought it would become the standard. However... it didn't
The big providers have been criticized by the Lead Dev of the OAuth 2.0 workgroup though. See this post from Eran Hammer: hueniverse.com/2012/07/oauth-2-0-and-the-road-to-hell/
