There's an article in today's Boston Globe called "BlackBerry: A high-tech ball and chain for lawyers." An excerpt:

"They are not just accessories or collectors' items," Brian D. Bixby, cochairman of the firm's private clients group, wrote in his memo, which became public after being sent anonymously to Massachusetts Lawyers Weekly. "They are not to be used only when you feel like sending an e-mail. They are supposed to make you more accessible for receiving e-mails after hours and on weekends."

..."while you are awake and breathing and not entirely engrossed in something else, there is no harm in having the BlackBerry on."

The firm draws the line at asking lawyers to keep their BlackBerries activated while they sleep, according to managing partner David P. Rosenblatt.