HTC handsets with the "Facebook experience" are reserved for AT&T only
HTC said their "Facebook experience" phones will be exclusive to the carrier. Now, nobody specified if it will be those same exact handsets as they are, or rebranded under different monikers. It also might be something totally new and Facebook-oriented from HTC further down the pipeline.
Nevertheless, if you love HTC and Facebook, AT&T will be the way to go, moreover these look the type of phones that are almost free on contract, so you've got a triple whammy here.