JupiterResearch has found that rising popularity of social networking sites and other forms of communication including text messaging and cell phone use are beginning to impact the effectiveness of e-mail marketing, particularly the numbers of consumers that say promotional messages inspired purchases.

The report (The Social and Portable Inbox: Optimizing E-mail Marketing in the New Era of Communication Tools) indicated that emerging forms of communication are leading to diminished use of e-mail. Twenty-two percent of e-mail users said they use social networking sites instead of e-mail, with scores more indicating they have used instant messaging (IM), text messaging, and cell phones instead of e-mail.

In 2007, 51 percent of e-mail users said e-mail inspired at least one online purchase, and 47 percent said the same for off-line purchases. However, in 2008, the share of e-mail users fell to 44 percent for online purchases and 41 percent for off-line purchases.