My mail provider locked my account after I used the satellite internet on an intercontinental flight (my IP location must have bounced all over). Got a serious scare later at my hotel since pretty much all of my itinerary plans and details were kept there.
Thankfully that could be resolved, but it wasn't a great way to start a vacation.
Oh and this can also happen when a mobile user is jumping off their home wifi network to a internationally roaming data card. Why they would do that? Because data is cheaper this way, or they are actually tourists. So please do not block users just because they are doing this teleportation dance.