Situational awarence is a key to success in any endeavor. Noticing what is around you at any given time can be of extreme value. It can be as simple as noticing a pedestrian attempting to cross the busy street, so you can avoid hitting him or her. Equally likely, it could be something so small one glance over it but not fully aware what lies beyond that Company Name, Contact Name, Email, and Phone Number.
Placing a card like this where people walk can produce a few phone calls. My current ratio is for every 15:1 i.e. I will get at least on 1 call back/text message for every 15 out. These fit very nicely in a targeted book at the Local Public Library, Barnes & Noble, Books-A-Million, or Magazine.