The meaning of the word "nerd" appears to have two very disparate definitions across generations.
Take for example the following example from work, an exchange between myself and an older manager of another department. I had my backpack, holding my books for my commute, my coffee thermos, and my work shoes (as we Chicago girls are wont to have). I can't come up with a better way to carry all that stuff. Anyway, she came walking up to me:
Manager: I saw you this morning with a backpack!
Me: yeah, needed somewhere to drop my shoes. Haha.
Manager: looks very...collegiate.
Me: er, yeah. That's me. Total nerd! Haha
Manager (serious): you shouldn't stereotype yourself that way.
So I take away from this that she wanted to ask something to the effect of why I had a backpack--was I going somewhere? When the response didn't compute, she felt the need to justify her question, thus the collegiate comment.
Now her definition of the word "nerd" is informed by a different era...a very different era...in which the "well rounded" student was the ideal. In this time, a nerd was someone who wasn't well-rounded, and this singled them out for the ridicule of their peers. Therefore, when I labelled myself a nerd, I was indicating to her that I was abnormal, a-social in some 1950s sense of the term, and she did not want me labelling myself as an outsider, a true retro-tabboo.
When I used the word, it was informed by a completely different generation. I was raised in an era of football camps, academic decathlon, and club activities that go all year long. It has been encouraged from day one for people of my generation to find a passion and run with it, often at the expense of other interests. For example: Sarah Palin describes herself (try to wrap your brains around this, folks) as a nerd, because of her passion for sports at the expense of being girly. Sarah Palin!!! It is cooler to be a nerd now, because it indicates enthusiasm, and you can be a "sports nerd," band nerd, computer nerd or math nerd arguably (and boy is it argued). Pop singers will pretend-blush in an interview and explain that they were total nerds in high school, because it is encouraged to be abnormal now. Hipsters like nerd cardigans, and athletes spend their summers studying pland improvin their technique.
I just want to put forth to all my readers the hypothesis that at least the connotative meaning of "being a nerd" has changed...but do I sound nerdy explaining it!!