Having been a mortgage banker for 18 years as well as an insurance agent for 5 years, here is how I see this boiled down.
The primary reason to have the properties in an LLC is for the protection of the corporate veil. In essence, its kind of like an additional insurance policy keeping your personal assets protected. Some people I work with will even go so far as to open an LLC for each home they own. This can be great protection but it comes at a cost. The cost is the time / expense / maintenance / additional tax returns of the LLC. For some, they don't mind the additional costs, so to them this is the correct answer.
Another way that people hold property is on a personal level. Now this is easiest and best for financing to a certain amount of properties owned, so great advantages that way, however a law suit then leaves all these assets exposed to a potential judgement.
No matter how you hold properties you really need to be insured correctly and with more than enough liability protection. What is more than enough liability coverage? Well the answer is that no one with any accuracy can ever tell how much you can be sued for? With that in mind, we then start with how much in assets do you have that needs to be protected? If any of the insureds is also a wage earner as well, then you need to protect 25-45% of the grass wages per year for at least 15 years. Most people forget about their wages, but in an injury judgement, all your assets can be exposed when you have exhausted your liability coverage. In that case, you are responsible for the judgement until its paid off, no other way to eliminate it. With that, you wages can be garnished, you bank accounts can be garnished, so everything you have can be at risk?
The best thing to do is set down with an agent that typically works with higher net worth clients, one that knows how to go through all your current and potential future assets, and then put together a package of coverages that will exceed your assets. Liability coverage is relatively inexpensive, so max out this coverage on your auto / home / toys and then follow it up with a properly sized umbrella policy. Keep in mind that defense costs are also covered over an above the liability limits on your policies. Defense costs can be very expensive, so this is another reason to have strong coverage there.
My guess is that you will find it less expensive to hold them personally and have soldin insurance policies in place, then to put them all in an entity such as an LLC. If you get to the point where you are maxing out on the numbers of financied properties, then consider taking a group of them and putting them in a commercial loan? Some lenders will not count as its in a another entities name, some will because you might have to personally guarantee the loan, so ask your lenders when you getto that point.
Properly insured, you should resolve the vast majority of problems and fears you might otherwise have? My 2 cents!!!