Update: This cap appears to already be official, though perhaps not yet enforced. The 10 GB limit is present as text deep in T-Mobile's Terms and Conditions page, listed in the "Protective Measures" section. Note that the limit is specified as being "subject to change" -- T-Mobile suggests that you check periodically for updates. The T&C document is dated June 28, 2008, but we know that the controversy over T-Mobile's earlier 1 GB limit came after that date, so presumably we're looking at some sort of dating confusion or conflict between this T&C doc and the original T-Mobile 3G document that specified a 1 GB cap.

Greetings. Back in T-Mobile Caves on 1 GB 3G Data Limit for HTC G1 Google Android Phone, I discussed how T-Mobile had retracted their published hard-limited (per billing cycle) 1 GB 3G data cap. After reaching this cap, users' data would reportedly have been severely throttled.

Rumors have been circulating for some time that a new cap of 10 GB was likely.

A source inside T-Mobile is now apparently confirming this speculation.

--Lauren--