Until now, the Google License has prohibited developers from using Google maps for intranet web sites - http://code.google.com/support/bin/answer.py?answer=55141&topic=10945
"The Maps API is not available for use within enterprise or intranet applications. "
Virtual Earth was the only available alternative for intranet apps. Until now.
Google recently released the new Google Maps API Premier , which allows companies to add Google Maps to their own website.
See the following:
"When Google Maps plays an important role on your public website, or is incorporated in an internal application for your employees, organizations need an enterprise-class application that handles high volumes and provides necessary support."
In terms of price, the Google Maps API Premier starts from $10K USD a year (based on the number of users). Virtual Earth has starts with Basic Platform Access (Incl. 200K transactions, 50 Users, 2 support incidents) for $4K USD per annum (I am unable to disclose their full pricing structure pending approval from Clint McCarthy at Microsoft).