Daniel Handler comments: "I think books have always been viral. Someone reads them and they tell people about them. That’s the best way to hear about a book." (þ: Grumpy Old Bookman)
That's how I hear about many of the books I read: via viral verbiage (sorry, it's his alliterative influence). The interesting thing is that when I go to Amazon, their "recommendations" are so rarely on target that I cease to look at them - I try to stay with Powells for my on-line book shopping. Ditto Netflix. It's far more usual for me to go to an on-line store looking for a specific author/actor and find additional items from there. It's a semi-serendipity, and I much prefer that to hoping that something they recommend will fit.
It goes back to the browsing question - yes, "real" stores may have less of a selection, but I get a better sense of whether the item is really for me, or if I'll give it a pass.