Attention avid video callers: according to early reviews, the new 3rd-generation iPad won't be able to make FaceTime calls over LTE. Given how popular we're all expecting the new iPad to be, I wouldn't be surprised if carriers put the lock-down on FaceTime in order to keep their LTE networks speedy. Alternatively, Apple may have set a high bar for FaceTime performance, and aren't 100% confident that LTE isn't reliable enough, even with its high transfer speeds when you've got coverage.
The funny thing is, you could use an iPhone as a portable hotspot to get FaceTime on the new iPad, or vice versa if you're packing an iPhone 4 and an LTE iPad with hotspot enabled. In any case, for the vast majority of iPad fans this is not going to be a dealbreaker. Anyone who's really dying for video calling through a cellular network can always pick up the Skype app for iPad.
Source: The Verge