I loved Dropbox when it first came out. Now I have Google Drive as part of my paid storage for Gmail, iCloud Drive for Apple devices, and OneDrive as part of my Office 365 subscription. I can't imagine any reason to pay for Dropbox.
For extra credit, the leader of the Google+ effort didn't use his True Name.
To extend this to the theme of the topic, while Google obviously displaced a lot of incumbents starting with the AltaVista search engine, do we expect this to happen in the future?