Estate Planning Attorneys as well as divorce lawyers frequently prepare pre nuptial agreements to help clients protect their property upon divorce or death. This is more common when the individuals have significant wealth or in second marriage situations.
It has been learned here Nick Lachey had asked Jessica Simpson to sign a pre nuptial agreement prior to their marriage and she refused to do so then they got married. With California being a community property state they are each entitled to half of everything the other earns during the marriage absent the prenup. While Nick had more assets going into the marriage Jessica has made significantly more since and her failing to have signed will now cost her tens of millions of dollars.
A video of their discussing the lack of a prenup can also be found here.