In reply to Clauso:
They might be teenage girls, virgins AND boulderers!
Always remember, no matter how bad your situation, someone else is worse off, having really drawn the virgin booby prize.
To revert to the conventional theory that these houris are teenage girls, presumably Allah can compel them to be sexually compliant, even to the most unprepossessing of jihadis. But this will not stop them continually, loudly and intrusively whining, moaning and bitching, because there is no force in heaven or earth that can stop teenage girls from doing that.
The ancient Greeks had a series of stories about the Gods having a warped sense of humour. One particular mortal was offered any gift by a Goddess, so chose immortal life. The goddess noted that he had failed to ask for eternal youth and beauty to go with it, grinned for a moment, and then said "are you quite sure about this?"
Mortal "absolutely, that is just what I want"
Goddess "well its your funeral"
Which of course it never was, given that he was now immortal. But he could and did get progressively older, more decrepit and miserable, being unable to die.
I rather suspect these jihadis, or Allah, similarly haven't thought things through enough, which is a bit of a problem when you are talking about eternity.