Interesting list. I think it's worth noting that these two groups have quite different charters ...
The ODF Alliance web site says that the alliance "works globally to educate policymakers, IT administrators and the public on the benefits and opportunities of the OpenDocument Format."
The OpenXmlDeveloper.org mission statement says that the community "will serve as a technical resource for Open XML developers to submit and answer technical questions and to share tools and ideas."
Based on those words alone, I think one could safely predict that the ODF site will probably name more companies than us in the future (policymakers tend to like that stuff), while we'll probably run more source-code examples than they will (developers tend to like that stuff).
- Doug