SatNav - where goest thou?

I have just had a visitor who complained about the road signs in getting to my house. Talking of the problem, I discovered that he had relied exclusively on directions given by his SatNav system. It directed him along a road which was converted to "buses only" about 6 months ago!
What worried me about this was the fact that my visitor proceeded to follow the directions of the SatNav and ignore the road sign! Why are we becoming so trusting of a system that we ignore the warnings that are put on the road? This is not the first time I have heard of drivers who disregard road signs; because the SatNav tells them to go a certain route, then they will go that way whatever the road signs are.

Personally, I much prefer using a map and thinking about where I am driving. I would never hand over control to some device. Perhaps it is because I work with computers and know their limitations.