I am not a lawyer, and I have not thoroughly researched this subject, so please do not hold my ignorance against me. That said...
I would strongly prefer that she sign a pre-nup (or something that accomplishes goals similar to the popular notion of a pre-nup). That way, if she decides to flake out on our family, we can *hope* to avoid *some* of the legal hassles that might otherwise go on for years. It would be better for us, and better for our kids. Of course, if she plans on being faithful and keeping her vows, then she shouldn't have any qualms about signing it.
The fact that they put airbags in cars doesn't mean that drivers want to drive into telephone poles. Rather, they are there to provide a measure of safety in the event of a disaster. I see pre-nups (or something that accomplishes goals similar to the popular notion of a pre-nup) as much like an airbag.
I want to avoid lawyers as much as possible if our marriage falls apart. Chances are good that if we are going through a divorce, we may be on the brink of financial ruin (as I've seen happen with others). The last thing that I would want to do is pay for some third party's new McMansion.
Before anybody questions why I have such an apparent 'lack of trust', please let me explain. I come from a functional family. My parents are still happily married after 50 years. However, as I look around, I notice that not all spouses even respect the institution of marriage.... and I also notice that people can change a lot over time. To top it off, I have seen the legal mess that divorce can cause. As such, I think it is only prudent to make arrangements that potentially soften the blow of divorce should it become our only option. To me, saying "I would never want to sign a pre-nup because it indicates a lack of trust" is much like saying "I would never want to drive a car with airbags because that indicates a desire to drive into telephone poles".