Re: 5 people editing one document simultaneously
It's actually extremely useful on corporate google docs, I don't know about Office.
You can configure "viewers" and "editors" so only approved people can change it.
Each user sees where the other users cursor/selected cell, so you don't really get conflicts.
There is only one version of the document in existence, so it doesn't accidentally get wiped out when Bob from accounts finally completes his section and puts it on the share.
You can chat to the other people viewing the doc, and they can see your cursor/position to see what you are talking about.
You can (just about) use it as a poor man's Trello.
However, the most commonly used example in our org is:
"Hi everyone. Can you fill in your row in this spreadsheet with your home working details over the xmas/easter/etc period please"