Back in the old days, the only realistic way to connect multiple remote sites was by T1 or T3 delivered either point-to-point or via Frame Relay. These were either slow and expensive or fast and unbelievably expensive. Then came MPLS, which dispensed with the need for point-to-point circuits from site to site, but was still bound by high expense. You got what you paid for. These circuits were not only reliable, but if a T1 or T3 circuit dropped, you could generally count on the carrier to jump on the problem quickly and resolve it with some expediency.
As cable and DSL networks began expanding, the ISPs introduced the concept of a business-class circuit. With significantly higher bandwidth than a T1 for far less money, these circuits are quite attractive -- but susceptible to the vagaries of their physical plant, which is to say that they're not as reliable as the T1s and T3s of old. In many cases, that trade-off is acceptable since the cost savings can be measured in the tens of thousands of dollars per year.
However, alternative ways to connect remote sites may enter the picture depending on their physical locations. The ideal solution is to be fortunate enough to find that all of your sites are served by a single fiber carrier, such as Optimum Lightpath. In other cases, you may find that your last-mile carrier (such as Verizon) has fiber to your locations, and a carrier such as Cogent can tie up all those ends into a connection served by a single end-to-end network. This way, you get bidirectional speeds up to 1Gbps between sites served by the same carrier, all for a lower monthly cost than a few 1.5Mbps T1s. If possible, this offers the ability to treat remote sites as local, enabling all kinds of replication and application delivery options that simply aren't available with lower-bandwidth circuits.
The new WAN: Weighing the options