From PCWorld.com:

Vinny Aceto, a Boston information technology specialist, is a 12-year veteran at helping fix people's PCs over the telephone and in person. Aceto says he has preferred telephone tech support over on-site service calls ever since he was attacked by a rabid PC owner.

"I was trying to explain to this sales manager [that] his hard drive was dead and I couldn't recover his presentation," Aceto says. The customer turned beet red, picked up his PC, and hurled it out his office window, Aceto says. The PC fell three stories and smashed to pieces in the parking lot. Next, the man jumped over his desk and tried to assault Aceto. Luckily people rushed into the office and stopped the attack.