Team building events in this economy is a luxury in this economy. One day or more devoted to building relationships can bring out the best and worst of people.
Most people will take the opportunity to lower their guard and interact with people they would not usually talk to.
There are a few people who dispute the opportunity will view the time as a day off and not learn anything at all.
In the end I believe team building events are not worth the time. Mainly because after these events after the glow of the events has left. Things go back to how it was before.