Here’s your thought for the day:
Think of Team Foundation Build build agents like shared, network printers in a large enterprise. Each printer can be assigned one or more tags such as laser, ink, color, duplex, or stapler. When it comes time for a user to print a document in the enterprise, they can require duplex laser color and the printing software will find an available printer that meets the criteria and send the job there.
Likewise, each build agent can be assigned one or more tags such as .NET4.0, .NET4.5, SQL 2012, Telerik, VB6, or VFP. When it comes time for an application to be built, the build controller will find an available agent that meets the criteria and send the job there. The only difference is that there is no walking up two flights of stairs to get your binaries.