Sprint's EV-DO data service was the only carrier to have truly unlimited 3G data, while AT&T and Verizon capped their service at 5GB. But according to a leaked update of their terms of service, effective July 31st, they'll be enacting a 5GB cap as well.

"Sprint reserves the right to limit throughput speeds or amount of data transferred and to deny, terminate, modify, or suspend service if usage exceeds 5GB per month in total or 300MB/month while off-network roaming."