Laptops, though, can consume people in so many different ways, which makes it harder to approach a conversation with someone. You never know if someone is checking email, doing work, or just social masturbating on Facebook. There is a thicker "invisible social wall" when trying to approach someone with a laptop because you don't want to bother something important, so very few people even try to start a conversation.
When someone's reading a paper, you know they are interested in the day's current news, which makes an easy conversation opener. You know they aren't busy doing their taxes or writing a paper.
Laptops on the other hand encourage communication with people not actually in the cafe, lowing interaction at the cafe.
Maybe a better middle ground was banning laptop use on a weekend beyond the quick checking of email, part of this would involve not allowing laptops to be plugged in.