Since the launch of the Thunderbolt cables over a year ago, there has been a subtle competition with the Universal Serial Bus (USB) cables. Thunderbolt cables offer 10Gbps of transfer rate while SuperSpeed USB cables only offer 5Gbps. In addition, Thunderbolt offers 10W of power through the cables to a device. However, the cables are much more expensive, $49.00 compared to $4.49, USB being the later. Recently the USB 3.0 promoter group has stepped up the competition and approved the power delivery spec for up to 100W over a USB cable.
The power delivery system has been designed to work with new and older cables alike. To accomplish this, the cables include an intelligent system to locate and check for USB wires and determine their capabilities. For example, a full sized cable would be able to handle 5A of current through it while a micro USB cable would safely be able to handle 3A. The system will also know whether it is working with a low quality wire to keep things as safe as possible.
In addition to the smart check system, the cables would be capable of switching direction of power flow. This can allow laptops to charge a device and also use it for a power source if necessary. While delivering power it will be delivered in steps between 10W and 100W, each one ideally doubling the one before. As a result, they can ramp power up or down between profiles. With much more power to work with now, USB ports on laptops can possibly double as a charging port. USB is looking to stay ahead of the competition and remain one of the most successful interfaces in the history of personal computing.
USB architecture (via USB.org)