Microsoft Office Live is not a web based version of Microsoft Office software (you know, Microsoft Word, Microsoft Excel, etc). It is in fact a service that offers collaboration tools for businesses, and some other services.
One of these services is the free domain name included in all Office Live Basic packages.
If you want to track how many people are in the beta (or an approximate number, since not everyone would have had a domain registered, I would have thought) there is a webpage provided by ipwalk.com that can help you on this.
Just check the Microsoft Office Live Domain Watch Page and you can see the advance on the number of domain names being registered through the new Microsoft offering.
According to Ipwalk, the watch page is updated daily, including a graph showing its growth since the launch of the beta. As of 3 March 2006 there were 8697 domains registered.
