(if you've never been to the Bay Area, the post below will make little to no sense. Be warned...)
For me, Kepler's Bookstore defined the quintessential Bay Area experience, before Silicon Valley, before choked highways, and before you could shake every tree in Menlo Park and have a VC fall out. On a bright and cool (and weren't they all) Saturday morning, you'd get on your bike and pedal over (exclusively on bike lanes) to Menlo Park to browse through what was the real "clean, well lighted place" for books. A happy hour, and a much lighter wallet later, you'd take your stash and walk out the door, and sink into a chair outside, holding your double espresso from Cafe Borrone right next door, and let the hours go by in a pleasant haze.
I am an online maven, and an amazon.com addict. I scorn old technology and the old ways, and am constantly restless for change. But I will mourn the loss of Kepler's, because the Bay Area will never be the same for me again.