• by Mark Walsh  @markfwal, May 5, 2009

Thanks to a "buy-one-get-one-free" promotion, Research in Motion's BlackBerry Curve overtook the iPhone 3G as the top-selling smartphone in the first quarter of 2009, according to market research firm NPD Group.

The Verizon Wireless two-for-one promo, which ran from Feb. 6 to Mar. 31, offered a second BlackBerry device of equal or lesser value for free with the purchase of any BlackBerry and a two-year service contract.

The giveaway helped propel RIM's smartphone market share during the first quarter by 15% to 50%, compared to the fourth quarter of 2008. The market shares of Apple and Palm, by contrast, each fell 10%.

A trio of BlackBerry models -- the Curve, Storm and Pearl -- ranked among the five most popular devices during the quarter, with the iPhone runner-up to the Curve and the G1 from T-Mobile and Google placing fifth.

"Verizon Wireless's aggressive marketing of the BlackBerry Storm and its buy-one-get-one BlackBerry promotion to its large customer base contributed to RIM capturing three of the top five positions," said Ross Rubin, director of industry analysis at The NPD Group, in a statement.

He added that the more familiar and cheaper Curve benefited most from the deal and was able to leapfrog the iPhone due to its wider availability among the four major wireless carriers.

Apple recently reported selling 3.8 million iPhones during its fiscal second quarter ending Mar. 28, helping the company beat analyst expectations. But that total was down from the 4.4 million sold in the prior quarter.

Don't expect AT&T and Apple to soon offer any two-for-one bargains on iPhones to grab back the smartphone lead from RIM, however. Subsidizing the iPhone at $199 apiece is already a costly proposition for AT&T, and Apple likely will not want to dilute its vaunted brand with more aggressive sales tactics.

The company can still console itself with the iPhone winning top honors last week in J.D. Power and Associates' 2009 wireless consumer smartphone customer satisfaction study.

Sales of both Apple and RIM devices helped expand the overall market share to 23% of handset sales in the first quarter, up from 17% a year ago. Smartphone owners made up about 13% of U.S. cell phone subscribers at the end of 2008, according to Nielsen Mobile.

"Even in this challenging economy, consumers are migrating toward Web-capable handsets and their supporting data plans to access more information and entertainment on the go," Rubin said.