I like to collaborate and I do it often. I collaborate when I design and deliver PBL workshops for the Buck Institute for Education, in my independent consulting work, and I certainly do it in my work with the Collaborative for Teaching and Learning. That being said, sometimes I'm a loner. Quite often I prefer to work from home instead of going into the office or at least wear headphones when I am in. The office is a busy place with people who talk to me and ask me questions and while I do enjoy chatting it's not always the most productive setting. As an educator I strongly believe in the power of collaboration but as Jason Fried points out in the video below, too much collaboration can be counterproductive.
One of the hallmarks (and criticisms) of Project Based Learning is group or team work. It's great to get students working with each other but if we place students in tables or pull desks together in squares and require them to stay that way throughout the project are we asking for trouble? A high functioning PBL classroom often looks messy with students sometimes appearing to be off-task (unlike adults who are laser focused 100% of the time in meetings and workshops right?) and some off- task behavior is natural. But placing students in an environment where they're forced to have to tune out the distractions that others can create for no real reason can be problematic.
Teaching students 21st Century Skills like collaboration is important but don't fall into the trap of trying to do too much of a good thing. Let your groups and teams breathe in an organic way that allows them to come together when it makes sense but work alone when the distractions of other students might slow the progress of your projects. When the time together becomes a bit more scarce you may just find that students level of productivity will increase, especially if the work they are doing is purposeful and meaningful.