I don't want to take anything away from the original poster, but the team at SCMSolution (www.scmsolution.com) has been providing a 100% hosted/SaaS delivered Rational SCM infrastructure internally to IBM/GBS and IBM external customers for the last 4 years. We've just spun off to our own company and are doing this for everyone. I'm not saying that WE are the world's first either :)

Check us out at http://www.scmsolution.com.