The area of federal purchasing that has most radically been transformed over the last few years is GSA's Multiple Award Schedules program. For many years GSA has served as the Sears catalog of the federal government. Now we are into real money. The idea behind the MAS program always has been to use the federal government's purchasing power to strike a better deal with contractors. GSA writes, negotiates and manages the contract, with offerings readily available on the Web.
Agencies make their choices.
In the past, the size of agency buys was limited. Similarly, restrictions on contractors' beating their own schedule prices prevented agencies from negotiating better bargains. Both of these constraints are history. In fact, agencies are now expected to get contractors to reduce their prices. Moreover, they can buy as much product and service as they want.