Not necessarily. Pepsi and Coke have both built quite legal relationships with a number of institutions like universities and fast food chains with the agreemen

Not necessarily. Pepsi and Coke have both built quite legal relationships with a number of institutions like universities and fast food chains with the agreement that competitor products are not served. My university was a "pepsi campus", you couldn't buy coke products anywhere on campus. This is why people have to ask "do you serve coke or pepsi?" at restaurants. Of course this has far fewer effects that social network tie-ins, but its not a new idea.