Another option is the use of API keys that are separated into two types -- partners and end-users. The partner API keys would be bound to a particular end-point

Another option is the use of API keys that are separated into two types -- partners and end-users. The partner API keys would be bound to a particular end-point (e.g., the IP address of the web server) while the end-user API key could be used from anywhere (e.g., from a mobile device).