It is always one person has their favorite team, then the team they like to bandwagon.
Example. A fan likes the jags, but knows they won't make it to the super bowl or even the playoffs, so he bandwagons another team he likes that is also winning, lets say the Falcons. It always happens, they either stay so low tune that they really don't feel like bandwagoners or they just don't care and will have 2-6 teams they like.
But that was when I lived in NY, here in VA its 100% loyalty or you are made fun of like a motherfucker. Being an eagles fan isn't easy here, way too many cowboy/redskins fans.