I would anticipate many IT professionals resisting cloud computing:
1) There is a perceived risk in not maintaining full control over critical data (weather valid or not),
2) Moving apps to the cloud could potentially reduce the need for an internal IT staff (self-preservation),
3) Connectivity between applications and other systems remains a significant issue in many SaaS solutions,
4) Tailoring an application to the needs of an organization to support proprietary tools, processes or other intellectual property that gives the organization a competitive advantage in their market space is easier to achieve in on-premises system today than in SaaS offerings on average. (This will change over time.)
5) Change is hard for everyone and physics reminds us that a body at rest will tend to stay at rest, resisting changes in its current state.