Thin clients without internal storage or software can replace full-on PCs. That approach pushes all the patching, user-configuration, security and other management tasks upstream to server-savvy technicians in the datacenter. Thin clients cost somewhat less than PCs, but the real savings come in reducing the number of systems that need the human touch. When someone's thin client fails, you just plug in a replacement and they're back to work, because the productivity software, OS settings, and authentication all live on the server. Plus, renegade users can't download spyware-infected games or smuggle out a corporate database on a thumb drive.

But thin clients do demand thick networks and powerful servers. Those requirements make the thin client impractical when your users work from branch offices, home offices, or hotel rooms -- there has to be a fat pipe carrying information between server and client at all times. And with little processing power of their own, thin clients aren't much use for intensive data-crunching applications.