Comedian Jerry Seinfeld once observed that with the way professional athletes change teams at will, rooting for our favorite team with its constantly changing cast of characters essentially amounts to the fact that we're just "rooting for laundry," i.e. the guys wearing our team's jersey.
Why do we root for some teams and not for others? Geographic proximity is the most common reason. I was born, raised and continue to live near Los Angeles, so I follow the Angels (of Anaheim -- don't get me started on
that issue), the Dodgers (to a slightly lesser extent), the Lakers, and the Anaheim Ducks. Had the LA Clippers done the logical thing and relocated to the newly built Pond in Anaheim during the 1990s, I might have been sucked into the black pit of
despair that is the lot of being a Clippers fan.
Note the lack of football teams on my list. In 1996, the NFL saw fit to allow both local pro football teams to depart, the Raiders back to Oakland where they belonged and the Rams to anywhere else where they, too, belonged. I'll start following real football (soccer) before I ever give a rat's ass about an NFL team again. From my high school days as a 155 lb., 3rd string linebacker, American football has proven itself to be a sport that I can live without. Even our local university, Cal State Fullerton, quit fielding a football team in 1993 and now sells "Titan Football: undefeated since 1993" T-shirts in the bookstore. Meanwhile the university's baseball teams are nationally-ranked every year and average a national championship every decade. Even the Titan basketball team made the NCAA tournament this past season.

Incidentally, I'm getting interested in NBA basketball (notably the Lakers) again after taking a few years off from the NBA culture. But I've followed the career of Kobe Bryant since he was drafted as a 17-year- old out of high school. At times, it has been obvious that his talent as a player far outstripped his ability be a good teammate or to make good decisions off the court. However, he does seem to be getting it this year, as he has elevated the level of his own game as well as the entire team's. In my opinion he is truly deserving of the league's MVP award and I've enjoyed watching his talent as he has matured and I'll continue to root for him, particularly on his journey through life.
Occasionally, other events have forced me to re-examine those loyalties as well. I was a die-hard Dodger fan growing up. When Rupert Murdock's Fox Corp. bought the Dodgers and replaced Orel Hershciser and Mike Piazza with Kevin Brown and Gary Sheffield I found it impossible to care about the team any longer. Since I had recently moved to Fullerton, just next door to Anaheim, it seemed like a good time to transfer my primary allegiance. Living just a 10-15 minute drive from Angel Stadium helps a lot, and as long as they don't sign Barry Bonds or Manny Ramirez as their DH (even though they seem to need one) I'll keep rooting for them, in spite of the fact that a sorting mistake with some of my red Angels gear could turn all of my laundry pink!