We require a Credit Card to start a 30 day free trial for our SharePoint 2010 plans for several reasons. The first is that it is an excellent way to filter out the best leads and support people who are serious about implementing SharePoint 2010 for their business. You can cancel at any time in those first 30 days without being charged a cent. If you want to continue using SharePoint past those 30 days, you don't have to do anything! and your account will automatically be billed and service will continue as normal.