It is common sense that when a sports team plays well it attracts more supporters. Nobody enjoys watching a team they like lose. Where's the fun in that? But if you are a diehard fan, you will stick by your team through the high times and the low. My sport is baseball and my team is the New York Yankees, and I stood by them even during the playoff drought of the 1980s and early 1990s. Yet even I arguably started out as a bandwagon jumper, when my dad took me to Yankee games as a kid during the championship days of Reggie Jackson and Ron "Louisiana Lightning" Guidry. Yes, some people become fans of teams that never or rarely win because it's their school team or it's the team their parents followed or their significant other is fanatic about, but for the most part, folks start connecting with a team when they begin playing well. They catch the bug, they get swept up by the fever, and suddenly they love the team and they keep coming back for more.
The test comes when the team inevitably hits tough times again. Does the newly minted fan stick it out through the dark days? Do they endure the seemingly endless losing streaks? Do they still go to games and buy the merchandise and call themselves fans when their team becomes a laughing stock? If they only think about their team when the wins pile up, what does that say about their loyalty?
Bandwagon jumpers are fine, that's how new fans are born, and many of them end up being loyal lifers, believing in their team through thick and thin. Fairweather fans, on the other hand, deserve to be ridiculed for their fickleness.
Then, there are people like me. I have my team, but I follow other sports and watch games when it gets interesting. If the Jets or the Giants or the Knicks or the Nets or the Islanders or the Rangers play well, I might watch their games and root them on -- but I wouldn't insult their real supporters by pretending to be a real true-blue fan on equal standing with all the fans who stuck by them for years. If the Knicks win a championship, I'll be extremely happy for their victory, I'll congratulate the real fans and celebrate with them. But I won't act as if they are "my team" and then if they start losing again some day flip-flop. (I'll just be honest as I always am.)
So my sister has a valid point about fairweather fans. But I encourage her and others to welcome bandwagon jumpers, frontrunners, or whatever you might wish to call them, because you never know, they might end up getting swept up by all the excitement and becoming just as loyal and diehard as the most fanatical fan. Show them some love, I say, and root for your team together while the times are good. There's always time for namecalling later -- it's more fun than watching your team lose anyway. :)