Confirmed: T-Mobile blocking GTalk video chat over 3G on Nexus S

Many Nexus S owners received a rude surprise when attempting to initiate an Android 2.3.4 video chat on T-Mobile's 3G network. Rather than being greeted by a smiling friend on the screen, a terse message explained "You must be connected to a WiFi network to start a video chat." Ouch. Doing the responsible thing, we tested the issue and were able to confirm that T-Mo is blocking this headline feature -- which worked just dandily over Sprint's 3G network on the Nexus S 4G. While the latest Gingerbread update includes built-in support for 3G video chat, Google has left the decision to mobile carriers whether to implement the functionality. We know choice is great, but when it ultimately hinders consumers, we'd really prefer an iron-fisted display of strength from Mountain View.

Android Central Forums, Google Mobile Blog