FTL writes "Tim Robinson has built a computer capable of solving polynomial equations -- using Meccano. His difference engine (mirror) uses a similar approach to Babbage's design. He's also created a differential analyzer (mirror) complete with a GUI. Both could be scaled up indefinitely to handle larger problems. 'Computing by steam' is possible."
Computers are unreliable, but humans are even more unreliable.
Any system which depends on human reliability is unreliable.