Even though an operating agreement is not required for an LLC in all states, you might consider it necessary. Even for a solely owned LLC, the operating agreement helps solidify your limited liability status. For LLCs with multiple members, an operating agreement pre-addresses many issues that could arise, from management to money issues.
If you do not have an operating agreement and a dispute arises between two members of the company, default rules apply which are established by the state. And which do you think is better, operating under the rules you wrote – or those of the state? Any entrepreneur should read Is An Operating Agreement Necessary for an LLC? for a closer look at this important issue.