Yes there is a huge argument for including people other than IT "specialists" in IT projects. Diverse teams provide diverse possibi lities,designers are very well placed to take on the role of bridging the abyss betweeen the social and technical, they have been doing so for a very long time, capably finding their way through extremely complex problem solving processes.... they are generally not phased by a seemingly insurmountable problem, indeed in many cases the harder the problem is the better, and this kind of thinking applied to IT can bring huge benefits.

Design thinking... is a term first coined by Tim Brown of Ideo in a Harvard Business Review article, where he outlines and advocates including "design thinking" in new and unexpected places.

The thinking was very succesfully put into practice by David Kester, Chief Executive of the UK's Design Council who has done some amazing work on this line with Ideo. Its described in the BBC radio4 program "In Business" which you can listen to here:
http://www.bbc.co.uk/programmes/b00jv9n0
you can find Tim Brown's original Harvard Business Review article "Design thinking" (that coined the phrase)here:
http://web.me.com/deatkins/CIC/Seminar_Schedule_files/HBR-Timbrown.pdf

Einstein said quite rightly "We cannot solve our problems with the same thinking we used when we created them" ... the more diverse and inclusive IT teams become, the better the results will be for all.