Conventional wisdom is that LLCs are a waste of time and money unless you have a significant full time business in real estate. Even small issues in properly administering the LLC for each property can allow a plaintiff's attorney to pierce the veil. Most of us are better off with umbrella insurance.
LLC formation is one of the most highly debated topics in real estate. The perennial argument is whether to form or not form and just use insurance.
Here's my point of view on what Snackdog says:
1) He's absolutely right that if the LLC is not maintained property or treated like an LLC then the corporate veil can be pierced. Search online for many articles that will state what can lead to piercing the corporate veil. Here's a short list: 1) Commingling funds, 2) Treating the corporate assets as your own, 3) Not following corporate formalities such as taking meeting minutes, annual report, etc.
2) In my opinion, the tasks in #1 are very simple. Keep a separate checking account, and keep great records making sure that it's treated as a completely separate entity. Do an annual meeting and report.
3) An LLC *is* a pretty cheap form of asset protection as far as I'm concerned. Unless you live in California. It's not a substitute for insurance, but when done properly, can be part of a greater plan to shield your personal liability.
While corporate veils can be pierced in certain situations, if the corporations are properly maintained, the veil won't be pierced.
And by all means, talk to a lawyer about the subject if you have any questions. A good lawyer's help in planning can also be incredibly cheap.