Core service (availability)

China's Great Firewall has blocked Dropbox since 2014 — at one point cutting users off from their own files overnight without warning — leaving the service reachable in the country only via VPNs that are themselves restricted.

To comply with US trade sanctions and embargoes, Dropbox does not provide service in regions such as Crimea, North Korea, and Syria — meaning users there can be cut off from their existing files by their provider's home-country law.