I response to WeekendWarrior's post, I did a bit of navel-gazing too. Not nearly as interesting as his thoughts, since I am LDS. But I didn't go to BYU, and it's still my number 1 team. Stop reading this loooong post if you like. But his thoughts about not being able to stop following BYU resonated with me. I'm a way bigger fan than any of my family members, and I didn't go to BYU. Even when I've been not as active in church, I've always been 100% into BYU. So I think I understand his feelings a bit.

There are many explanations for why I am a BYU fan, but it's harder to explain how I became such a dyed-in-the-wool one. I also tried to cheer for other teams at times, none really caught on — I might like a team or coach or player — but my soul was never in it — other than UCLA as my alma mater, and then it still wasn't the same pure, in my DNA, totally part of my core feeling as with BYU.

Despite going there and being a big fan, I wasn't born-and-bred UCLA; I still feel a much stronger pull for BYU in FB, to the point I cheer for BYU against UCLA (even the year they played twice in Football, when I held UCLA season tickets and went to the bowl game). 59-0 was glorious, but it also hurt. I wished it was more respectable for my #2 FB team. But push-came-to-shove, there was no scoring play where I wished BYU wouldn't score again, no time when I wanted UCLA to come back and close the gap, even as I was a bit embarrassed by their play.

I follow and support all UCLA sports — and I don't necessarily keep up with BYU women's softball, gymnastics, etc. So, for other sports I didn't follow as a kid, maybe I'm a bigger UCLA fan than BYU. But BYU FB was my first and greatest college sports loyalty — probably only eclipsed by SF Giants baseball in all of my childhood sports fandom.

Biggest reasons I became so attached:
(1) my grandpa went to the U, but he became an ardent BYU fan (and did not then and still does not like the U) — somehow the converted to BYU and attends every game idea just made me think BYU transcended where you went to school and that the U was little brother (none of my other grandparents went to BYU, one went to USC and one to Berkeley/UCLA (when it was two campuses of the same school, but all were LDS and at least positive about BYU with only 1 out of the 4 having a tie to the U)
(2) my parents and siblings were mostly BYU fans, although they were also mostly casual supporters and not really into sports — I was way more into it. But I think it became part of my identity and I just took it to the next level. I was going to be a better fan than my parents because was raised in it.
(3) some of my best friends were BYU fans. This was a big influence. Having grade school and middle school friends to watch games together with made it more a part of me, bigger than just a family thing.
(4) BYU was good, often excellent, fun to watch most of the time, and covered by national press in a way that no other home team anywhere else I had lived was. There was no other team I had such strong ties to and cheering for anyone else made me feel like a fake.
(5) being LDS was a big factor; I wrote letters to SI protesting or correcting their portrayal of BYU as being misinformed or having an anti LDS slant. I felt offended by it deeply by media treatment of BYU, not just at a fan level, but at a religious identity level too.
(6) my coolest uncle — the youngest one who was the most fun — went to the U, but was never really into sports. He'd played high school football but didn't really care much about the U — was a fairweather fan of both BYU and Utah, with an edge to Utah. Despite being a big influence in my life, he did nothing to evangelize Utah sports to me at all, and seemed equally okay with supporting BYU. If he were strongly anti BYU, I wonder what effect that would have had or if he would have been the cool uncle. By contrast, my most colorful, black sheep in the family uncle (in and out of jail, lots of WoW problems) was a big BYU fan. His misbehavior didn't turn me off BYU; instead, it — along with a lot of other things — made me think that he had a really good heart somewhere and that at least he was anchored despite all of his issues.
(7) it helped that Steve Young and Bart Oates played on the 49ers, who I also loved, and that tied my pro and college loyalties together.