Prenups

For some states that have community property laws, this may not be as relevant since anything acquired by either spouse during the marriage is considered joint property, and ideally the assets brought into the marriage is owned by the the individuals.  Still, this is an important consideration considering the average divorce rate in United States is more than 50%.

The overall goal of prenups is to " provide the less affluent spouse with the comfort of knowing that an end to the marriage doesn't necessarily mean an end to the lifestyle to which he or she has become accustomed."

I personally am not 100% sure about the goal of prenups, but it does offer someone with significant assets comfort going into a marriage.  Although it can protect the less affluent spouse with comfort, it also in may ways can protect the affluent spouse the comfort that their significant other isn't just after their wealth.  In either case, I believe it keeps both parties honest.  

Discussions about a prenuptial agreement may be the first opportunity you will have to communicate with your partner about money. Like it or not, money is one of the things that most couples fight about, and financial matters will likely play a big role in your married life. These discussions can be an opportunity to lay the foundation for a secure future, or even present the chance to realize that you almost married the wrong person. (source)