I wonder how many virtual companies are out there.   With the explosion of the internet, the barrier to start a company has been all but removed.  A minimum requirement could be a web presence. With an online connection and an abundance of workgroup and communication tools, one or more people can start a company overnight without even being in the same town.  Companies don’t need an office building if the people involved are self directed and are disciplined enough to communicate via phone/mail/im and other tech tools.

Here are some more references on the subject:

Virtual Company Advice
Becoming a Virtual Company
Art of running virtual companies
Palmedia-Virtual Company Solutions
Why I started a Virtual Company

The employment needs of talented professionals with home-based responsibilities are not being met despite the low unemployment rate