Via the NYT. This is why e-mail marketing is not for the faint of heart:

A typical information worker who sits at a computer all day turns to his e-mail program more than 50 times and uses instant messaging 77 times, according to one measure by RescueTime, a company that analyzes computer habits. The company, which draws its data from 40,000 people who have tracking software on their computers, found that on average the worker also stops at 40 Web sites over the course of the day.