Ars Technica:

The ITU recently established that 4G technologies have a minimum of 100Mbps speeds while a client is in motion and up to 1Gbps speed while stationary.

Clear’s WiMAX has a maximum bandwidth of 50Mbps with real speeds of around 3-6Mbps. Verizon’s LTE: 5-12Mbps. T-Mobile’s HSPA+: 3-7Mbps. Clear, Verizon, and T-Mobile do not have 4G networks. They are technically lying to you and in the process poised to make a lot of money. How much? In Verizon’s case $50 per month for 5GB, and $10 for every 1GB after that.

Update: MG Siegler:

Danny Sullivan notes the difference between the iPhone 4S and the Galaxy S II Skyrocket on AT&T. Both are actually running on the same network, but the Galaxy gets the all-important “4G” moniker.