CircleID

I do not believe Enum will be all that useful with out an authentication system that validates the origin of calls. It's all well and fine to be able to resolve the destination of a call across the Internet using the standard numbering plan. But the question will become should we accept a particular call from the Internet. This is a problem that has NOT been solved for email yet.

Authenticate against whom?  Have one single entity that controls your signon? All due respect to your comments, it's highly inpractical.  With ENUM being so similar to DNS, how would you verify that all DNS queries are legit?  You can't(yet).  But we all take it for granted that when we pick up the telephone to answer a call, that the caller id info is correct.  You are correct that this could be a problem, (spam anyone?) and no solution has been ratified for email.