How email and social media influence purchase decisions

"Kantar Media Compete's study also found that nearly one in three consumers receive more than 20 emails from retailers in a week. And in good news for retailers relying on email, 89 percent of respondents at least occasionally click through to a retail site from an email or visit a retail site immediately after reading an email.
SMS, on the other hand, is still a largely untapped channel for brands to reach shoppers. During a typical week, three out of four consumers (72.2 percent) don't receive any text messages from retailers.
Do social networking sites influence purchase decisions? Yes. In fact, 35 percent of respondents say that Twitter feeds have been influential or extremely influential on purchase decisions, while 23.5 percent say that Facebook has been influential or extremely influential on purchase decisions."
Source:  Data from Kantar Compete, published in a press release, 13th September 2011
Note - All data is for the US only