Desktop computers are getting smaller, but Chip PC Inc seem to have taken it to the extreme with the Jack Pc. This is a thin client PC built into a wall socket. The idea is that you replace the Ethernet socket on the wall with one which has the whole computer built into it, then you plug your screen, keyboard and other peripherals straight into the wall socket.
A computer in a wall would have a few advantages: it would be harder to steal and would save desk space. This could be particularly useful in classrooms and computer labs. However, instead of just two cables from the wall (power and data), there would be numerous ones to peripherals. The computer box on the desk acts as a cable concentrator. Also it would be much harder to maintain the Jack PC as you would have to remove it from the wall (but then perhaps thin clients do not need much maintenance).
Chip PC also sell desktop thin client computers.