Wireless carrier Sprint announced yesterday that it would no longer be offering unlimited 4G mobile broadband for mobile hotspots, USB modems, tablets and notebooks. Formerly, customers chose one of three plans which offered 3GB, 5GB or 10GB of 3G data and unlimited 4G data. The changes, which will take effect in November, will now only allow 3GB, 5GB and 10GB of combined 3G and 4G data, charging 5 cents for every additional MB of data above the allowance.

The move is notable not because data caps are uncommon, but because Sprint, the third largest wireless carrier in the U.S., is the last remaining provider of unlimited data plans for new phone subscribers. Its 4G unlimited data plan has been a large element of what has kept Sprint competitive with AT&T and Verizon, whose networks are larger, but who no longer offer unlimited data plans to customers whose plans have not been grandfathered in.

Though smartphones have not yet been included in Sprint's plan changes, the abrupt shift away from unlimited data in other devices - a feature Sprint CTO Stephen Bye called a differentiator in the carrier marketplace - suggests that the toll of such an offering may be too costly for Sprint in the current climate. In its efforts to raise capital for its 4G LTE network launch next year, Sprint is accumulating a heavy debt, and unlimited data offerings may not be a long-term option. If they are, unlimited plans could potentially lure users of the iPhone - which launched on Sprint on Tuesday and is an especially data-hungry device - away from Verizon and AT&T. However, The Street reports that some Sprint subscribers have complained of slow speeds since the iPhone 4S's launch on Sprint on Tuesday and Sprint will have to work hard to maintain the same level of service in the face of even greater numbers additional users.