Now I said a while ago that Single Canonical form wasn't for SOA well now I've been doing some SaaS projects and I've realised with traditional modesty that not only am I right, but that people who are still pushing it as an approach can be described as suicidal dinosaurs.
If SaaS is anywhere in your future, and it will be unless you are a military secure establishment and even then it might me, then GIVE UP NOW on the idea that you can mandate data standards in applications and create a single great big view that represents everything. It isn't going to happen, you are now back in the wild old world of multiple different systems each with their own specific exchange formats and....
you have to cope with it
Moaning about it or trying to push back on it because it doesn't meet your "corporate data model" isn't going to get you very far, its liable to get you heading out the door in fact.
Single Canonical Form is for people who believe in the great big database in the sky theory of architecture, it didn't work for SOA but some people still tried to force it in. Now the love child of SOA and the Cloud is coming to destroy it completely. The only sensible policy is to look at an "active" MDM strategy and a brokerage approach to communication between systems ideally based around a federated data strategy that leaves information its its source systems but provides references between them.
The brokerage challenge and active MDM challenge will only grow as SaaS becomes more common. There is no ability to inflict, and I choose the word advisedly, your Single Canonical Form on SaaS providers so you have to actually take a sensible solution oriented approach to data consistency and visibility.
Single Canonical Form is a dinosaur like approach but it was one which some people still managed to get away with proposing as a way to create a career. Well SaaS is the meteorite heading towards their earth and the choice is evolve or die.