If Canonical wanted a contributor agreement which crafted protections against misappropriation of contributed code in bad faith, they could have that. Such language is possible. The reality is Canonical specifically wants the ability to proprietary re-license as part. I simply can't fathom why.
Now I can sort of understand that if Canonical actually owned the copyrights to something significant that could be relicensed and sold as a proprietary work, But they don't. They aren't sitting on a functional codebase like mysql or a full framework like Qt. What they have are bits and pieces bolted on a larger framework they don't control over and I just don't see how anyone is going to bother paying for a proprietary licensed version of any of their in-house developed stuff.
Bzr as a proprietary re-licensed thing? Upstart as a proprietary re-licensed thing?
The utouch stuff maybe has some life in it as a proprietary relicense if they try hard enough to sell as a quick fix for touch capability in a proprietary application. More likely people are just going to route around having to purchase this tech.
I'm not even sure I see the copyrights they do own as value-add in a possible acquisition by another company. Launchpad my have value in an acquisition as a running service...but owning the copyrights isn't where the value is in that case.