I am one of those people who have eclectic tastes and are in the middle of reading about a dozen books. I like having a long list of my favorite books available at all times as well -- sometimes I want to look something up right away. I am also the most intense,
always-reading-a-book reader I know (by a small margin in a few cases) although I know there are many here that can match me.
And I am fine with the Kindle's 2 to 4 GB memory, since I can hold from 1000 to 3500 books on it.
I have my 170-book TBR on it, I have all my favorites on it, and I don't need ludicrously expanded memory to do it... I wrote a scathing post about it somewhere, I will see if I can find it.
Not that it is a bad thing to have the space. I simply don't see it as a make-it-or-break-it feature.