Savas Parastatidis links to an article he co-authored about this subject.

I strongly believe that there actually is a difference between SOA-style Web services and Distributed Objects, and I even share some of Savas’s thoughts. But I don’t think WSDL is a good candidate for making this point, since with its reliance on XML Schema it’s probably the least flexible and most static part of the whole Web services architecture.

Update: more here