Careful, this is starting to sound a lot like 'they all even out by X'.
I understand Clay's point because I, too, have one of those kids who was talking in complete sentences by 6 months and I'm not talking about made up words but real sentences. I was over at my mother's house one day and was exhausted since my crazy baby did not nap so I took advantage of the extra hands and crashed on my mother's bed while my mother and grandmother played with DD. They were begging her to take a nap and pointed to me in the other room sleeping. DD wasn't having any of it and said "I'm not my mother." Very clearly and meant it. She was also asking her "what's this" and "what's that" questions none stop at this time. YET out in public she was tight lipped and hardly ever said anything. Only when she was distracted by something that excited her did she forget where she was and open up which was met with open mouths and complete shock by strangers. And btw, may just be my experience but have noticed how this attitude extended into school time and DD's need to just fit in.
This said, I know a few people who exaggerated their children's speech ability and one in particular couldn't remember half of what she told people. One day her daughter was talking crazy sentences yet by age 2 she hadn't formed a sentence and needed to be tested, etc. It got to the point that I took in the information with a wait and see approach. But this is also a person who is VERY competitive and was clearly trying to hothouse her child. Whenever she heard stories from others about what their child was doing she ran home and set up shop to teach curriculum to her daughter even though her daughter had shown no interest in anything she was trying to teach her.
