ITBusiness.ca has a good article entitled Fire your outsourcer! that talks about how important it is to negotiate and draft outsourcing agreements that contemplate ending the deal from the outset.

This is true for any arrangement where one contracts out a function, or hires a third party service provider, even if it is not technically outsourcing.

There are any number of reasons why one might want to end such an arrangement. The point is that it is far easier if the arrangement contains transition provisions, and if the service was set up in a way that is transition friendly. Even if one does not change, it gives more bargaining power if the service provider understands that the transition barriers are low. A modern version of not wanting to owe one’s soul to the company store.

For more detail, read the ITBusiness.ca article