There is such a thing as too much nerdiness. Oh yeah, just roll your eyes at me--I'm at Tech, the center of nerdom--but I'm not kidding. There are those people who keep asking annoying questions in class, but it's worse when they're actually not asking a question. They're just rambling about what they think they know. And the professors just nod and smile and privately think, "Stupid kid." This gets worse with graduate students.
Additional Commentary:
This appears to be universal. It's extremely bad when graduate students who think they know it all start arguing with the professor. (Argument is good--constant agreement is a sign of complacency--but just to argue to show off your brilliant "deductive" skills is just plain egotistical. Yes, I know you read a gazillion papers each week, but I do too and I don't claim to have an encyclopedic knowledge.)
On the other hand, maybe this egoism is a product of a brilliant mind. Perhaps my observations only give more evidence that I am only average. There are plenty of bright scientists out there who are, shall we say, a bit unhinged.