Many of you may already be aware and using the feature in Google Apps where you can simply attach something from Google Drive, rather than uploading it from your desktop. It is a great feature and probably the future of sending files. Very simple concept: Don't attach the file, but share it with recipient. When you hit the send button, it even tells you the document is not shared with the recipient and offers to automatically share it with them- still a very wonderful feature.
However, you need to be aware that by default, it make the document public and that anyone with the link to it can see it, even if they are not the recipient. You will be shocked later to find out you have documents that are publicly accessible. In one case, someone had a scan of their passport and was sending it to another internal person, used that option and it was only discovered thanks to the audit report generated by
GAT (General Audit Tool).
Our recommendation is to select the option so that only the recipients of the email can see it. Otherwise the entire world can potentially see what you shared.