GMs and World Builders write a lot, so keeping things organized and making a very efficient system helps save time and focus on the more fun aspects of the hobby.
In Google Docs you have a permanent history for the document.
Footnotes. If your fond of researching and wikipedia, footnotes are your friend. I learned the value when I was writing for a group and I needed to cite my sources (and had to learn the value of sources etc.) Category: Insert > Function: Footnote/Endnote. I used alt+down.