If you have a lot to lose, heck yeah!
You never know what's going to happen after a marriage. People change... Spouses cheat... I wouldn't want to lose half of my assets because my spouse turned out to be a cheating beech.
And if she's not willing to sign the pre-nupt for that, then it throws into question her own motives for marriage... If she's in it for love, then half of my net worth shouldn't be of interest to her...
I think this is a theoretical discussion, and not one to be concerned about particular state laws which may forbid the practice.