Verizon is offering $200 off the Apple iPhone 4's retail price to those who bought Android and BlackBerry smartphones late last year.

The little-known fact was discovered in Verizon's iPhone 4 FAQ section by the eagle eyes at Boy Genius Report, and is clearly aiming to placate annoyed customers who bought a Verizon smartphone right before Verizon's official iPhone 4 announcement last Tuesday:

"Current Verizon customers who purchased and activated new smartphones, feature phones or certified pre-owned phones between 11/26/2010, and 01/10/2011, are eligible to receive up to a $200 Visa debit card when they purchase an iPhone 4 at full retail price by 02/28/2011 and return their existing phone. Note: This offer is only available on consumer accounts with five lines or less, who are purchasing iPhone 4 through Verizon Wireless retail stores, telesales, or through verizonwireless.com."

Verizon's full retail price for the iPhone 4 is $649.99 for the 16GB model and $749.99 for the 32GB one, which means you're still paying around $450 for a 3G, CDMA Apple iPhone. And before you think "eBay," don't forget you'll also have to hand in your old smartphone.

Last Friday, online ad network Chitika called the Verizon iPhone the "biggest threat to Android." In its study of online mobile traffic, Chitika said the majority of Android traffic comes from Verizon.