Aspiring authors, published authors, and non-authors alike, do yourselves a favor and take a moment to check out Ben Yagoda's essay in the New York Times on readers' access to writers in our technological age.
I can only think of one occasion that I've done it on a purely personal level: I was trying to recall the title of a beautiful novel I'd read in college (Bapsi Sidwha's Cracking India) that had been titled one thing when originally published, another in the US, and a third when made into a film. Upon googling, I stumbled across the author's website. Uncharacteristically, I took a moment to reach out to her and say how fantastic her book was and how much it had stuck with me. And I was delighted when, over a year later, she came across my email and realizing she had not thanked me, wrote back.
Since I haven't done it again, apparently the reward of hearing back wasn't enough to encourage me (though by that point I was an agent, and ethically it had become more complicated) to continue reaching out. Obviously the examples in the essay are the odd, amusing, or frustrating ones, but do any of you routinely contact authors of books you've read? And published authors, what emails do you get to rival Mary Karr's love letters from the incarcerated?