A recent article in Consumers Reports featured a blind test of online legal documents by three law school professors. Their conclusion:
Using any of the three services is generally better than drafting the documents yourself without legal training or not having them at all. But unless your needs are simple — say, you want to leave your entire estate to your spouse — none of the will-writing products is likely to entirely meet your needs. And in some cases, the other documents aren’t specific enough or contain language that could lead to “an unintended result.”
Bottom line is people don't know what they don't know, so they have no way to judge the quality of legal documents on their own. This particularly a problem for Wills and Trusts, where the deficiencies may not come to light for many years. Caveat Emptor!
See this post on the article by attorney Robert Ambrogi.