TL;DR Google Docs are very good for casual, not to long documents, which you do not intend to print out or where formatting is no primer. Collaborating with MS Word and Google Cloud Connect is also handy, as long as you have no fancy tables, headings, footers or many graphics. For bigger documents and workers using MACs, Microsoft Skydrive rocks.
I happen to work in academia and most of our projects are understaffed and sometimes they lag behind schedule. In order to profit of economies of scale, to get our job done when things become hairy, our boss throws more personnel at the projects. This works well, as long as those human resources (read: my colleagues) can collaboratively work on documents. Dealing with documents is the daily bread-and-butter job description of a post-doc these days.