WiFi sniffing is one of the least productive methods for hackers to compromise your account. First, they have to be almost in the same room (WiFi doesn't travel that far,) have some software that would seem curious in an internet cafe, and be able to spend quite a bit of time hanging out waiting for the person logging into their bank account or business account.
Far more productive is to sit on the wired side of the connection (i.e. the connection from the cafe to the rest of the internet.) Using the same tools that are used to debug Ethernet connections they can read 100% of the traffic. Now it is true that on an HTTPS connection that traffic is encrypted but not all people on the link nor all interactions will be via HTTPS.
My personal view is that most of these hijacks are inside jobs. Like running illegal drugs the potential payoff for a programmer at Google for downloading a few thousand account names and passwords could be pretty big. Consider that Bradley Manning (assuming he did it) got access to and downloaded thousands of secret communications simply because he was "upset."