A Quora user recently asked, "What distinguishes M2M from previous online applications?, and gave a specific example: why is the London oyster card system not an example of M2M?
In fact, I had recently answered a similar question (Internet of Things: Whats the difference between the "Internet of Things" (IoT) and "Machine to Machine" (M2M)?) this way:
On the Internet of Things, communications and transactions are between a "Thing" and one other actor -- either a person (which is what happens most of the time on the "regular" Internet, or another Thing). When the other actor is also a "Thing", the system can be called M2M, since both parties are machines, and they are communicating with each other as peers.
Applications like the Oyster card system don't really fit this mold. While the actual sensors are "managed" in a sense by some kind of server infrastructure, they act more like peripherals communicating with a host controller than dedicated actors communicating with another actor as peers.