WCF 3.5 will support Usernames over Transport Authentication
Like Dominick Baier and Christian Weyer of Thinktecture, I also wondered why I couldn't use a UsernameToken with Transport Security in WCF v.1. I wanted to put together a simple demo for a client and that feature just wasn't there. Dominick mentions in this post it will finally be available in WCF 3.5. Great!