Consumers who previously owned a smartphone are far more likely to buy an iPhone than those who have not. This, according to a report from NDP Group a provider of consumer and retail market research information for a wide range of industries. NDP was studying the effects of the Apple iPhone release into the mobile phone marketplace in the United States.

Palm’s Treo and the T-Mobile Sidekick have been hit hardest by the release of the Apple iPhone. The Treo is a highly popular smartphone with plenty of downloadable applications and built-in functions as well. The T-Mobile Sidekick has been a popular internet connectivity device combining web browsing, email and IM.

Early iPhone buyers were 10 times more likely than other mobile phone buyers to have previously owned a Palm Treo according to the NPD Group report. These same early adopters of the Apple device were about three times more likely to have owned a T-Mobile branded phone, such as the Sidekick.

The defections of customers off the Treo and Sidekick devices to the iPhone speaks to the value of the Apple device as perceived to meet the needs of these users somewhat better than the current devices. Though T-Mobile is quick to point that the Sidekick offers full featured browsing it falls far short of the experience the iPhone

offers in the full featured Safari browser with multi-touch control. The Treo, arguably the best phone for productivity does not offer the “cool” factor of the iPhone and as the pressure mounts for downloadable applications for the iPhone the usefulness of the Treo over the iPhone will become an arguable point.

“The iPhone’s internet and media capabilities have resonated with consumers - especially those who previously owned Treos and Sidekicks,” said Ross Rubin, director of industry analysis at NPD. “Its advanced operating system makes it competitive with smartphones for many tasks, while its sleek design and lack of expandability is reminiscent of fashion phones.” The competitive nature of the iPhone in the smartphone market is yet to develop a full head of steam since the applications available for performing some of the functions the Treo comes packed with are limited. There have been, however, many examples of the Web 2.0 applications providing for some of this functionality.

One note of interest is that Blackberry sales have thus far gone untouched by the iPhone revolution. It may be the push nature of Blackberry email (and the lack of iPhone corporate email support) that users find so addictive, but whatever the case it is good news for Research In Motion (the creators of Blackberry) that these devices have so far gone unscathed.