[citation][nom]apocalypseap[/nom]I bet they're doing this just because of the stance they took on porn-related applications.[/citation]
More than likely - no such services sprung up in the UK when 3 launched video calling years ago, but then the technology never took off over here. Plus the cameras weren't up to scratch and the network wasn't fast enough - let's just say my ex-gf's video calls we're up to a required standard.
Given the number of iPhone users in the US with better cameras and (supposedly) faster networks, there's probably now a viable user base and tech to do this.