When I was in college, I had a stubborn teacher who absolutely demanded that certain parts of our project (Web site / application) open in new windows. I tried to explain to him why this was a big no-no. He didn't understand.
Maybe I was at a loss for words. Maybe not. But today I found the most amazing, concise and compelling explanation -- I just couldn't have said it better:
Visitors want to have control over everything what happens in their browser. If they’d like to open a link in a new window they will. If they don’t want to, they won’t. If your links open in a new window you make the decision which is not your decision to make.
Thanks to these guys for the explanation. I will burn it in my memory for future projects -- there will never be a shortage of bozos attempting these shenanigans.