I setup an LLC for my side projects and consulting a couple years ago. Since then, it has evolved into my consultancy that I now do full-time (in fact, my latest creation, LeadNuke, is a "product of Alfa Jango, LLC", and may be spun off if I decide to take any investment for it).
Forming an LLC really is not very difficult, and it's good practice to get started early if you plan on going full-time at some point. More importantly, the clarity boundaries it provides to your business expenses and taxes is worth the effort alone.
Single-person LLCs are legit and can protect your personal liability IF you run it like a legit company. People who form single-person LLCs have a tendency to get lazy with record-keeping and procedures. Don't fall into this trap. If someone sues you, and the judge looks over your records and says, "Yeah, but you didn't do anything differently than if you hadn't formed an LLC," personal liability protection is gone. This means, setup a separate business bank account for ALL business income/expenses, sign ALL contracts with your business name, make sure clients address checks and issue your 1099s to your business name, etc.
Concerning insurance, I wouldn't bother unless you're working on a project that has the potential to lose a lot of money if you do something wrong. If you work on an ecommerce application for a company that will be doing $50k or more sales a month through it, perhaps insurance starts looking like a good idea (god forbid you accidentally leave their merchant account in test mode when you deploy, and no one catches it for a week).
If you do get insurance, what you actually want is called Errors and Omissions insurance (liability insurance is for if you have a physical office and you want to protect against your equipment if there's a fire, or if a client visits and slips and breaks their arm). If you get E&O insurance, be sure to shop around, many of the big insurance companies won't do it for you, because of how new and unknown the web-based software industry is, so you might have to go with a smaller local insurance company to work out some policy that fits your needs.
EDIT: I should clarify that in Michigan, forming an LLC is incredibly easy. I'm not sure about California, if that's where you are.