The way extensions work is that you can enable an arbitrary number of sync providers all at once. So you can have Dropbox enabled, Google Drive, maybe you even

The way extensions work is that you can enable an arbitrary number of sync providers all at once. So you can have Dropbox enabled, Google Drive, maybe you even have a webserver on your computer so you run an extension from there that writes to your local disk - you can sync to all 3 of these at the same time. So it doesn't have to rely on a centralized server.