Chica Chaser beat me to this.  It is a fairly well known feature of Shiite Islam, or at least I thought it was.  There is a certain element of comedy in it from out cultural standpoint, but from a Shiite standpoint it is a very serious matter indeed.  
See the following for some references, including cites to the Qur'an:  
http://www.thereligionofpeace.com/Qu...y-marriage.htm
http://en.wikipedia.org/wiki/Nikah_Mut'ah
It is not only for instances of prostitution, but also for instances of cohabitation without sexual intercourse do ease the requirements of modest dress (
hijab), when a married man moves away for long periods of time to another country and will be separated from a spouse.