The chief benefits are that the information is more easily available outside of the enterprise, that the effort of providing services is basically just turned into a cost, and that the application can be scaled up to the organisation's needs at the turn of a switch.
What are the main disadvantages though? It must be harder to integrate a cloud based solution to the ever present in house systems that lie in every organisation. Since the data is based in an external system there could be large limitations on getting access to that data.
The cost of the solution as well might be more easily changed by the vendor meaning that the IT organisation has less control on the total IT spend than they would for an in-house system.
Information week published an article today on Cloud Chaos, stating basically that because Cloud solutions don't necessary require IT buy in to start their use, soon enough an organisation could have multiple cloud based solutions that don't co-ordinate well either with each other or the in house software again.
Given that Forrester's projections show that in 2009 almost 10% of IT Management software could lie in the cloud, it is a good idea that organisations plan ahead for the challenges that cloud computing represent