At a high profile CES Event, a key WP7 employee delivered, in an off comment fashion, a few tips about where the platform may be headed. One feature that was discussed was that Microsoft is working on a FaceTime type like application for Windows Phone platform.
Now we have confirmed the news that Microsoft is working on a Apple iPhone's "Facetime" competitor, a feature of the platform that allows the user to make video phone calls to other users of the iPhone.
The registry keys "VoIP" and "SIP" are hidden inside the "ControlPanel" portion of the registry, and both seem to be set to be off (by having "0" under their "Enabled" value). It's worth noting that for some reason, these keys are in a portion of the registry that contains other features that are fundamental to the platform, such as theme colors. Right now, we don't have write access to the registry to attempt to turn it on, but hopefully in the near future the homebrew community may allow us to do this.
The VoIP feature has not been revealed before, and it is not certain whether or not this will be used for the "Facetime" like feature, or if it would be available for actual VoIP calling to other Windows Phone 7 users.