What is a Google Doc most useful for?

Google Docs are for Collaboration and this is helpful when a sample group of people / Team work together. You can view & edit and as I heard from the Google team 50 people can work together. For me, our IT team finds it handy that instead of sharing over emails, one version over another, just finish by collaborating.

Working on a collaborative project remotely -- the group doesn't have to be all in the same place to work on the document at the same time. Also the work history gives a detailed account of who edited the document and when it was edited.

Google doc is most useful for staying organized with co-workers. I can easily keep co-workers up to date with my progress when we are working on a project together.