Email remains the most potent, popular, and productive marketing tool, with the highest ROI ($40.56 for every $1 invested in 2011).
Buyers say they prefer to receive promotional messages by email (77%). This paper gives tips for building your email marketing lists
with real-world and social tactics, and helps you decide when and how to buy a list.
Excerpt
...Twitter is a smaller audience, but it has the largest amplification effect. People who tweet daily are creating
content at the rate of two to six times others (frequency, not quantity). Research shows that people on Twitter feel
anxious about the persistent messaging and fear missing out; appeal to this group with a message amounting to:
"Email is the one way you know you won’t miss out on things from us."