The master branch's version of DotNetOpenAuth currently does not cache identifier discovery information even for the length of an authentication, resulting in two discoveries per login. (DotNetOpenId 2.x does not have this problem).

We should definitely build in discovery caching before the release of v3.0.

This has been working for a while (beta 1 has it right). We're leveraging .NET's built-in support for HTTP request caching. This works equally well for HTTP and HTTPS requests, so we're even faster than DotNetOpenId 2.x, which didn't leverage .NET request caching, since 3.0 will use caching to avoid even the first discovery during authentication if the user has logged in before.

I have updated the comment on verification discovery to indicate this in commit 2371d9cc.