One problem that I've seen over and over again in my last 25 years of practicing estate planning law, is the unfunded or underfunded Revocable Living Trust. What do I mean by this? Well, time and again I've met with a client who comes into my office with their late parent's fancy and impressive looking living trust documents only to find out that there were little or no assets at all that were actually ever transferred into the trust after it was created.
When I then have to explain to them that this is going to result in the parent's estate having to be probated or formally administered, needless to say they're typically not too happy to hear this. The lesson to be learned can be summarized by the old idiom "you get what you pay for." Namely, there's a reason why you should have your trust prepared by a reputable estate planning lawyer and not a do-it-yourself or some kind of online legal help service.
Here's a short video that I came across where the attorney does a nice job of explaining why the funding of a living trust is often the most important part of the process. Take a look.