Here is my 2 cents:
There are numerous land border crossings between the US and Canada (assuming that is what you are referring to). There are number of booths on each crossing and there are a number of people who change shifts and work at these booths. Me and my wife cross the windsor-detroit tunnel 5 times a week and been doing that for a year now.
To this day, I can never say that there has been a consistent questioning procedure. I can almost relate numerous variety of questioning that I have experienced and 99% of them have been a normal courteous exchanges. Based on this, I think that if someone mentions that a certain thing happened to them, that may not necessarily reflect a written policy of the immigration and custom services of either of the countries. It may only be the dicretionary action of that border official over that particular individual on that day.
In other words, to this day, I have not seen anyone noting the passport number or stamping the passport (again, in my particular case only).
Here is an experience. This officer at the US entry point saw my wife's cancelled visa and asked why her visa was cancelled, even though, if he paid attention (maybe he did), he would have seen "Cancelled WITHOUT PREJUDICE" on the visa. He then found another active visa. Even though we do not need a stamped visa to enter (we just happen to have one from our previous lives!), he decided to check her H1B validity and punched in those numbers in his computer. A week or so later, we happened to go through his booth and he simply waved us through without even looking at any of our documents.
As far as I am concerned, those two actions of his were solely based on his discretion.
So, people, take your documents and have a fun border crossing without fretting too much. Take care.
