I have a real soft spot for cafes, up to the point of working in one for about a year as a grad student just for the hell of it (Nefeli for you Berkeley denizens). Recently I've been meandering throughout Evanston getting most of my work done at Mud, Liquid, and Unicorn. I'm a multiple visit per day type of person. Name a cafe in Evanston, and I've been in it.
Recently, I've been feeling, not quite ashamed, but odd pulling out my laptop. There's now a teeming horde of laptop folk. It's gotten to the point that you'll have pairs/couples working across two laptops at the same table.
Well back in my old stomping grounds, Jon Snydal, Damon McCormick, and Sean Savage are investigating this effect, among other things, with Project Placesite. I couldn't quite put my finger on what was bugging me until I read their exposition of The Zombie Effect. Publicly staring deep into a virtual world that others can't join in is probably a muted form of the public cell phone conversation effect. Of course, I'm a prime offender.
Oddly enough, I'm not sure this is actually a problem per se. Two of the cafes I frequent are essentially startups, and I know they would be seriously struggling if they didn't have a stable of Zombies drawn by free wi-fi. Plus, I don't particularly find laptop folks any more or less approachable then say snobby looking folks reading The New Yorker.
Last point, Evanston would make a very interesting case study on the commercial impact of Wi-Fi on small vendors, especially cafes. We have a local incumbent which, seemingly reluctantly, moved to for pay access. This despite heavy usage by a CS department and tons of laptop carrying undergrads. (Aside, our VP of IT claims 80% of our frosh came to campus with a laptop. Yikes!) Meanwhile, the aforementioned upstart cafes have arisen, along with Wi-Fi in a few other sit down spots, plus the deployment by the big boys like Barnes & Noble and Borders. I don't know if the slow move to Wi-Fi made a difference on Unicorn, but I see a lot of customer distribution to the new places.