I beg to differ with the three of you. I don't believe that you can pull a trailer in a business and not be required to have it FULLY insured.
Check into this because every state I have had trailers and plates in, you are required to have insurance on a trailer when it's being used commercially. Matter of fact, anything you use commercially in the process of producing an income for your business, must be insured under the business name and insured properly.
Now if you are just be-bopping around with a trailer you are using, not for the purpose of generating income with, then you may not need insurance. But if it's your business, I'd certainly have the thing insured.
And yes, it's expensive to insure things. Why do you people think we have to average $70.00 per hour or more in order to make it in a legit business. There are a lot of costs involved. None are as expensive as not having your equipment insured and getting into a major accident.
Insurance is however all a racket. Insure it today, get into an accident, then they either raise your rates or they cancel your insurance. There's no winning with insurance and the insurance companies know it. My two cents.