Some will never say no, even when something is unworkable. There is also the problem of the outsourcers' over-optimism.
Time differences can also be a difficulty.
No matter how good the communications infrastructure, if the offshore facility has a big time difference, the window for interactive communication may be small. This can be turned into a virtue though. As a customer you have to plan better. IBM turned time differences to its advantage when it used offshore development services to develop its VisualAge Part Pak two years ago. IBM split development over five sites in Seattle, Asia and Europe, taking advantage of the different time zones to run two shifts, enabling 24-hour development.