The key thing to remember about MPLS is that it’s a technique, not a service. MPLS can and will be used to deliver anything from IP VPNs to Metro Ethernet services.  Albeit carriers build MPLS backbones, the services that users buy may not be called “MPLS”. They could be called anything from “IP VPN” to “Metro Ethernet" or whatever the next buzz word might be at the time of print. 

The bottom line is that network operators can use MPLS to deliver a wide variety of services. The two most popular implementations of MPLS are layer 3 BGP/MPLS-VPNs, on a router level, and Layer 2, on a switching level.