If you ask them beforehand, you get a self-selecting sample, biasing your result. You get better results by not asking them.
replySure, you're right.
replyI was rather commenting on the tone that Thoughtworks decided to "take 10 engineers and put them in one room". I took that wording literally, imagining how they grabbed these 10 engineers with a big hand and dropped them off where they wanted them to develop their airline IROps system.