One example is the Hola VPN which, in itself, is a VPN that uses other users' connections to act as a VPN to almost all countries, but they also sell access to this network of IPs via https://luminati.io/.

Basically like Tor, some VPNs route someone else's VPN connection through your VPN client. If I want an IP address in Sweden and someone in Sweden wants a US address some VPN companies would just route our traffic through each other's home addresses (potentially leaving you on the hook for what the other user was doing).