As silly as this may sound, the type of furniture and seating arrangements have the largest impact on the amount of collaborate that takes place.

In America we operate under the personal cubicle as the pinnacle of the workplace. The cubicle is great for focused work but is awkward for spontaneous collaboration. Architecture school also operates with the cubicle mindset with each student having a personal space and/or desk to work at. In some of these environments I've found quick collaboration between peers to be difficult or non-existent.

In a studio I took over in Germany, the entire studio collected around one large table with everyone facing each other (computers and all). Not only did interaction between students increased, but the time spent throwing around ideas, suggestions, and quick spontaneous collaboration increased as well. The furniture layout was the most conducive to having people collaborate together.

If you really want to encourage collaboration, you need the right furniture and layout to do the job. Say no to cubicles!