!!! Overview
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* No [Discovery Mechanism]
* Mandatory [Authentication] of the [Resource Owner]
** There is nothing in [OAuth 2.0] about [Authentication] ([OAuth 2.0 NOT an Authentication protocol])
* No [Authentication Assurance Level|Authenticator Assurance Levels]
* No information on the [Resource Owner]
* No [Logout Process] (Well since we did not [Authenticate] why [Logout Process|Logout])
* Some folks imply that there is a [Authentication Double-Hop] issue.
* Allows [HTTP GET] for [Authorization Response] which has [Data Leakage] issues. [OpenID Connect] formally defined a [HTTP POST] response mode. 
Most of these short comings are addressed within [OpenID Connect]

!! More Information
There might be more information for this subject on one of the following:
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