I did telemarketing for about 2 weeks once... I went in out of my mind though, [not going into any specifics, but neither the customer or I knew what I was talking about by the end of the conversation] and walked out. I can tell you though, I loved it when the customer would put the phone down. I hardly made commission anyway, so that was just a nice break to be able to sit there and do nothing. They tried to keep us offline by removing the icon to internet explorer from the desktop, and the start menu [no seriously], so that was easy enough to figure out... So really setting the phone down may hurt the actual company... but may make the agent's day. I mean really, would you rather have to talk to the next pissed off customer, or sit and play games and read news?

Granted, I was young and had no respect for my employers time/money... but it is kind of hard to respect a telemarketing agency.