sfEntrepreneurs kicked off Sunday evening and one of the first questions we faced was how the 20+ of us would be able to efficiently communicate in a form other than email. This was a question we continually face with beRecruited (people in San Francisco, Seattle, Atlanta, Boston) and faced at eBay.
We decided to use WikiDot.com for a couple reasons, and I've been generally happy about the results thus far:
1) Google Docs work well for specific documents - but they don't scale over time well... more importantly the documents are treated distinctly and ultimately get as cluttered as your computer desktop
2) Wikis are ideal for concepts that intend to grow (new pages are easy to create and are woven together intuitively)
3) Wiki technology is less intuitive than Google Docs - but the core functionality takes only a couple minutes to learn
4) Wikis are easier for group contributions (from small edits to major additions) and for group watching
5) Wikidot (like Google) enables private domains and customizable layers of control, invitations, etc - critical for internal discussions