It's the dose that makes the poison

From "Too Much Information? Ignore It" (Alex Williams, New York Times, 11-11-07):

After reading Mr. [Timothy] Ferriss’s recent best seller, The 4-Hour Workweek, Jason Hoffman, a founder of Joyent, which designs Web-based software for small businesses, urged his employees to cut out the instant-messaging and swear off multitasking. From now on, he told them, severely restrict e-mail use and conduct business the old-fashioned way, by telephone.

“All of a sudden,” Mr. Hoffman said of the results, “their evenings are free. All of a sudden Monday doesn’t feel so overwhelming.”
...
“BlackBerrys and e-mail aren’t inherently bad,” [Ferriss] said. “It’s just like medicine: it’s the dose that makes the poison.”

The 4-Hour Workweek web page