From Lambda Legal:
Darrin Ellis and David Arriaga were in a committed relationship for five and a half years. On August 14, 2003, Ellis and Arriaga met with their attorney to execute estate planning documents and their Declaration of Domestic Partnership. Arriaga was to send the notarized form to the California Secretary of State's office, and Ellis believed Arriaga had done so. It was not until the relationship ended in 2006 that Arriaga informed Ellis he had never mailed the Declaration of Domestic Partnership to the Secretary of State. Ellis filed a petition for Dissolution of Domestic Partnership (the equivalent to a divorce) on September 8, 2006. On October 24, 2006 Arriaga asked the court to dismiss the petition, arguing that no domestic partnership had been created because he never sent the notarized form to the Secretary of State. The trial court agreed with Arriaga's interpretation of California's domestic partnership law and dismissed the case on February 2, 2007. Lambda Legal is appealing that dismissal.
[Lambda Legal Staff Attorney Tara] Borelli noted that people in different-sex relationships who believed they were married and have lived their life as married only to find out later that their marriage was not valid are protected by California's "putative spouse doctrine."
Boreli said that Lambda Legal will argue that California law should protect domestic partners similarly, and that the trial court's interpretation of the domestic partnership law raises serious constitutional questions.
So, basically, domestic partnerships are not the same as civil marriage, and aren't getting the same protections.
Just another reason why we need full marriage equality. They can make up words like "domestic partnership", "civil union", or "coconut mango chutney", but in the end, all they're doing is beating around the bush, not using that one word that, when performed by the government, does not refer to a religious ceremony, and creating legal havoc that only leaves same-sex couples legally inferior with a whole lot of litigating and contracting and proclamating and affidaviting to do. What GLB Californians have is better than nothing, but it's not the same as what heterosexuals like The Lockhorns enjoy.
Kay, I'm done preaching to the choir for now.