Please stop that PC nonsense. Marriage is ownership -- they have a monopoly on each others sexual-ability and in the event of a divorce they will properly have to split the money fifty-fifty.
Marriage does not imply "monopoly on each others sexual-ability" (unless you mean marriage in strictly christian terms, for example), this is up to the partners to decide.
Yeah ... 'cause I'm sure a guy that just became a multi-billionaire didn't have a prenup.