A coffee shop I used to frequent [1] tried to take a "soft" approach to that, by having a sign near the electric outlets under the tables, asking patrons who were going to stay longer on their laptops to spend at least $n/hr (I don't remember what $n was). So people who didn't use the outlets didn't get bothered, and those who did got some guilt pressure to either buy things or not stay all day. I don't have any inside information on how well it worked, though. And this was a few years ago, so maybe that particular trick wouldn't work as well in these days of 10-hour MacBook Air batteries.
From chatting with a few managers in the Santa Cruz area (not sure how representative a market it is), they didn't want to actually drive away the laptop crowd, because that provided the majority of their business for much of the day. To some extent they wanted to be a coworking type of space, because there's no other way to fill up a coffee shop in Santa Cruz or Capitola at 11am on a Tuesday in November. They just wanted the laptoppers to either keep buying stuff periodically, or else keep their visits somewhat reasonable (i.e. not 8 hours on one coffee).
A different place I used to work at [2] actually liked me staying around all day, whether I bought something or not, on days when it was mostly empty, because it helped give the impression that the place wasn't deserted. They did most of their turnover on tourists, though, so there was sort of an informal agreement that laptopping regulars should move along when the place was full (mostly weekends or summer afternoon/evenings).
From chatting with a few managers in the Santa Cruz area (not sure how representative a market it is), they didn't want to actually drive away the laptop crowd, because that provided the majority of their business for much of the day. To some extent they wanted to be a coworking type of space, because there's no other way to fill up a coffee shop in Santa Cruz or Capitola at 11am on a Tuesday in November. They just wanted the laptoppers to either keep buying stuff periodically, or else keep their visits somewhat reasonable (i.e. not 8 hours on one coffee).
A different place I used to work at [2] actually liked me staying around all day, whether I bought something or not, on days when it was mostly empty, because it helped give the impression that the place wasn't deserted. They did most of their turnover on tourists, though, so there was sort of an informal agreement that laptopping regulars should move along when the place was full (mostly weekends or summer afternoon/evenings).
[1] http://www.cafeugly.com
[2] http://www.mrtootscoffee.com/