Some users keep several versions of Drive in their /Applications folder by renaming them. Problem is, the FinderSync extension loaded by the system is the one of the first .app added. If newer .app are launched, the extension won't be up-to-date and can be incompatible.
We cannot block people from putting more than one .app in /Applications, but we can prevent them from running it.
If the app is run from a folder other than /Applications the extension won't be properly loaded by the system. We have to prevent it as well.
When we detect one of these situations, we'll display a message on startup and force quitting.