Assuming the couple signed a prenuptial agreement, as most wealthy Californians do, Zuckerberg and Chan would have agreed exactly how to split assets, including his Facebook stock, if their marriage dissolved in future. Even without a prenup, the wedding’s timing would help establish the value of their assets in the event of any future divorce battle, lawyers said…

Had they continued the status quo, Chan could potentially lay claim to a much larger portion of assets, including a chunk of his $20 billion in Facebook shares, lawyers say.

“In California, people who live together without the benefit of marriage could claim they had an agreement to pool resources and efforts,” said Napa, Calif., lawyer Robert Blevans. Although they are hard to prove, “those claims can get really ugly.”