There are some things that fall clearly within the parameter of being a a "true" sports fan: Knowing your team's last championship, being aware of its strengths and weaknesses, and sticking through patches when they suck, for example. Some necessities are murkier, like knowing the entire offensive line or remembering your squad's ABA history. Of all the prerequisites to being a "true" fan, few are the source of more arguments than having an extra team to root for.
The most obvious argument against having more than one team involves the concept of loyalty. On the one hand, people get whacked for shit like disloyalty. But at the same time, sports is supposed to have some leisurely appeal to it, right? Being a Knicks fan is admirable, but what are you really going to get by being austere in your fandom? Daps? You sure as hell aren't getting a championship any time soon.
The second-team may be excusable for extreme cases like these. Sometimes a fan's love of sport transcends one franchise. When this does happen, however, there are rules. If you're interested in picking up a second helping of fandom, allow us to guide you through The Ten Commandments of Choosing a Second-Favorite Team.