For Verizon Wirelessended the most successful first day sales in the history of the company with its pre-orders of the iPhone4. For smartphone users, however, it was a day to complain bitterly. That’s because Verizon Wireless began reserving the right to slow down data services for subscribers who consume exceedingly more than others., it was a day to celebrate. On Feb. 4, the telecommunications giant

According to a document on the company’s website, subscribers who sign a new contract for an unlimited data plan — a necessary step to buy a Verizon iPhone — are agreeing that the carrier may throttle their data speeds if they use so much data that it slows down service for other users.

"This is looking ahead and making sure that our customers get the experience that they expect from us," Verizon Wireless spokesman Jeffrey Nelson said in a statement. "We all have seen what happens when a company doesn't manage its network."

Although Nelson said Verizon’s decision to throttle speeds won’t extend to subscribers who signed their data-plan contracts before this week, carriers capping data speeds is nothing new. Back in October, TechZone360.com reported that T-Mobile put the brakes on its high-speed data gobblers. A company statement revealed that starting Oct. 16, T-Mobile will begin reducing data speeds when a customer exceeds 5GB of data usage in one billing cycle.

T-Mobile is assuring customers that the measure – put into effect to “ensure that all subscribers receive the best Web performance available” – will impact less than 1 percent of data users and that the majority of T-Mobile customers will not be affected by the new policy.

In the meantime, the general market launch of the iPhone 4 on the Verizon Wireless network will occur on Feb. 10. The company will open its more than 2,000 Verizon Wireless Communications Stores at 7 a.m. It will also be available at all Apple store locations, Best Buy, select Walmart stores, and online at www.verizonwireless.com and www.apple.com.