I know a local fortune 500 company that tried this at one of their two buildings here at their corporate campus a couple years ago. Well, they are back to a desktop at every cubical now because they found if something happened, like a switch went down, suddenly all 100 - 200 terminals on that floor was down and no one could do anything until it was back up. With desktops, they may not be able answer emails, but they could at least still use office and get something accomplished if the network went down. You take 100 employs making 20/hr sitting and doing nothing for 2 - 3 hours and you've bought yourself the cost of the PC's.
To be honest with you in my office and most offices I work in, if they loose local switching they loose phones, and access to all applications and databases. At this point you should pretty much send everyone home. Citrix,Vmware View, and windows terminal session broker all support HA/Fault-tolerant clustering options on the back in. Throw in a duel controller replicated SAN and you can push 5 9's of fallibility all the way down to the desk. Get 2 hour replacement support on switching or standardize and keep a spare. Virtual desktops reduce management, and downtime ins a massive way. I used to work in a SMB with 60 task workers, who after we went to virtual desktops with no-moving-part thin clients I had so little support work to do that I quit, and recommended that I not be replaced.... Its true RDP sucks for a lot of things, but if you have sufficiently fast storage on the back end and use modern protocals like PCoIP, HDX, or the up and coming remoteFX you can have a true desktop experience (I even played starcraft 2 over RemoteFX).