Re: How important is application integration?
I think the focus has to be on the employee's user experience. Collaboration works best when it is in the flow of work, not separate from it. There are tools designed specficially for collaboration, but at the same time almost evey major enterprise application either has or will soon have some level of collaboration capability built into it. So the question for many businesses will not be which collaboration tool to buy but how to agree on where, given the many tools they already own, they will do their collaborating.
The problem can be mitigated somewhat by technolgy through integrations that expose discussions and activity streams across multiple platforms, but this can only go so far. Ultimately I think a company or business area will need to form an agreement among employees that "this is where we do our work."