So if I do not use their wifi (use my evdo card instead) and sit there forever with a single cup of coffee, is it ok? Or am I supposed to buy their wifi instead? I am confused about your reasoning.
Would it be OK to sit there forever reading a book after buying a single cup of coffee? I would say it depends.
In this case they don't charge for the WiFi, it just comes with your coffee.
My reasoning is that most laptop users will use WiFi, and if they want to use it, they at least have to ask for a new card every couple hours, which involves either buying something or overtly seeming like a leech.
