It is always a good idea to make a will. Although the law of intestacy provides for the distribution of your assets if you die without leaving a will, making a will (or trust) allows you to decide who should inherit from your estate. This can be especially important if you are married but have children from a prior marriage. In California, the law of community property can result in those children receiving little or nothing if you fail to leave a will.
Stewart-Williams v. Williams
Here is a recent example from a California Court of Appeal decision. This should not be construed as legal advice or a complete statement of California law on this subject. This is merely a case illustrating how the probate courts deal with community property of a deceased individual who does not have a will.