OpenID, how to develop a provider

Developing an OpenID Provider as a means of Single-Sign-On (SSO) within an organizations ring of web sites is a very valid scenario. DotNetOpenAuth comes with a pair of sample web sites (a Provider and a Relying Party) that demonstrate a single-sign-on relationship. They're called OpenIdWebRingSsoProvider and OpenIdWebRingSsoRelyingParty.

Please do not attempt to implement OpenID by yourself any more than you'd implement SSL by yourself. Getting OpenID security and interoperability just right takes a very long time and a deep level of domain knowledge. DotNetOpenAuth in particular gives you programmatic access to do just about anything you'd want to with OpenID, and since it's free, it's hard to go wrong.

Disclosure: I am a developer behind DotNetOpenAuth.

Actually my question is: can anyone become an OpenID provider and is DotNetOpenAuth a library to develop this protocol in your own infrastructure?

if you're think you can do it, you can follow this:

Lastly, and most challenging, is implementing custom support for OpenID in your software and account management tools. While this approach of course affords the greatest degree of control over the user experience, it is also the most risky and only for developers experienced with web security. Start by reviewing the specs and documentation.

But my question would always be:

Why one more provider? Facebook, Google, MyOpenID, ... already have it, and with them, plenty of users have (even without them knowing) an OpenID login...

StackExchange is an OpenID provider since a while ago, but... there's so much users cross StackExchange platform. Are you developing such a big community so it will be reasonable to create and implement your own provider?