I work for Microsoft. Before bing 80% of internal search engine traffic was to google. The reason MS employees used google instead of live search was pretty much the same across the company - live search sucks.

However, MS employees finally have a decent search engine made by Microsoft. Bing is good. There are 100,000 employees that likely just switched from whatever they were using before to Bing. That might affect the stats a bit. Plus, those employees will tell their friends and families.