Far and away, the most common question I get asked when talking with anyone about "outsourcing" and a distributed workforce is what can and can't be done with a distributed team.
The reality is that most things can be done, just maybe not the way you currently do them. There is no room for messy, half-baked processes with this.
Tasks that require a high degree of collaboration aren't necessarily suited however they can be if there are clear 'stations' that a piece of work stops at and if each individual knows what is required. At Skyrocket SEO (of which Cohortive.com is a part) almost every task from highly-collaborative such as infographic production to client contact is handled remotely. Teams work from home or in shared workspaces in their hometown.
The immediate reaction to new tasks is often concern as to how practical achieving X, Y or Z virtually is going to be, the reality is often very different once a process has been carefully tweaked.