Join Date: Mar 2003
Location: anywhere and everywhere
Programs: United Nations 193, UA GS, AS MVP 100K, DL Diamond, Marriot Lifetime Titanium, AmEx Centurion
Posts: 6,362
Not most countries, but most border crossings.
About 12 years ago when training for a marathon, I decided to run back and forth on the bridge over Niagara Falls, crossing the US/Canada border (and flashing the passport) over 20 times. By the 3rd/4th time they were annoyed, but by the 10th or so they were simply amused.
Would never try that these days though.