Sprint has announced that subscribers activating smartphones on its network on or after January 30, 2011 will need to subscribe to a $10 Premium Data add-on feature. Previously, this add-on was only required for 4G phones. For those considering Sprint, particularly those interested in a 3G smartphone, we suggest signing up before January 30. Otherwise, you’ll be on the hook for an extra $240 over your two year contract. Compare Sprint rate plans and cell phones here.