If you have assets that amount to more than what your car insurance and home insurance coverage provides, then you should probably get an umbrella policy for protection. The amount of umbrella policy coverage you should have is an individual choice. If you want to be safe, get an umbrella policy equal to your estimated net worth.
I’ve personally taken a “riskier” approach by getting an umbrella policy less than my net worth. I figure, I’m not doing anything particularly offensive or risky in day-to-day life, nor is my business putting anybody in physical danger. If I was running a roller coaster amusement park on the other hand, you bet your buns of steel I’m getting maximum coverage!