According to the founder of Instapaper, a popular Web and mobile service that allows users to read website content offline, the introduction of Verizon Wireless’ iPhone 4 may not be pulling many new customers into the iOS ecosystem. Marco Arment speculates that sales of his popular Instapaper app are likely a good barometer for iOS device sales. Arment finds that app sales see “huge spikes” when Apple releases new iPhone handsets, thanks to the flood of new iOS customers that purchase the phone. When Verizon launched its iPhone 4 earlier this month, however, Instapaper sales were unaffected. Arment poses three possible explanations: Verizon hasn’t sold many iPhones, Verizon iPhone owners don’t purchase many apps compared to other iPhone owners, or Verizon iPhones have been sold mostly to individuals who had previously owned iOS devices and therefor are able to simply transfer previously bought apps to their new phones. He feels the third scenario is the most likely. Arment’s theory is not necessarily supported by sales data revealed exclusively by BGR earlier this month. Alongside launch-weekend sales figures from five major Apple Store locations, we revealed that only about 14% of Verizon iPhone 4 buyers had previously owned AT&T’s version of the Apple smartphone. It is worth noting that data from our exclusive report did not include sales made at Verizon Wireless store locations, however, and it also did not include buyers who had previously owned the iPad or iPod touch.