If you, like myself, rellay like the Google Drive and it’s abitlity to co-operate on a seamless basis no matter what operating system or office version the other parties are using and if you share entire folders or certain files with people from time to time it can after a while become rather difficult to keep track on these shares.
Maybe you sometimes share with someones email address or you may share a link to the document with a bunch of people. It is a good idea to go through your shares and revoke all that are not supposed to apply any more from time to time.
There isn’t’ an easy builtin tool to do this into the Google Drive but I hope we will get this one day. In the mean time there is an additiona tool that you may use: https://whohasaccess.com/ which is a third party app that will (after your permission) scan your google drive folders, create a report on the permissions you have set.
You can then use this report to review your sharing options and change them accordingly and when you are done you may also delete your data at the third party.
However, if your data is really sensitive you should think about using a third party app like this access to it. But if it is normal personal stuff we all put together and it’s not something that is sensitive commercially or worse it is a pretty good feature. I do hope Google Drive people would include this function in the normal Google Drive menu soon however. The service resides in Germany and is thus bound with the data protection act of Bundesrepublik Deutschland which is a little comforting.