Originally Posted by
Cityflyer10
I'm guessing he was referring to US passports which pre-GE, was very hit or miss (well, mostly miss) for me.
Most countries don't stamp their own passports.
The US *usually* stamps foreign passports when arriving by air (excluding trusted travelers) but not always. As pointed out above, CBP has a fully electronic scheme for keeping track of how long foreigners stay in the country.