There are people out there who can talk the paint off a wall, sound utterly brilliant, and they're still of no real use to anyone.

Very true. I've met a few who sound lucid and intelligent by their word choice, but have no ability to manage the critical thinking that should go with the vocabulary. These people are truly, truly, scary. Kind of like Sarah Palin. She is beautiful, she speaks clearly, but she is not always lucid, she speaks nonsense. Some people listen to her and think she has a message. She doesn't.

I've met others who aren't public figures, but still, are problematic in the disconnect between brain and mouth.