My 9-year old niece is a fanatic of a local loveteam. She watches their noontime show daily and begs her parents to buy their magazines, albums, and even the products that they endorse. Should we tolerate this behavior?

If you have the means to support her interest, then for me, it is fine to tolerate this behavior. After all, most of us went through this phase during our childhood and teenage years. I even remember, I was such a fan of an international boyband for years to the point that I save my allowance for the purpose of buying their posters and albums if my parents won't spoil me. Despite this, there is still a need for parents to open up conversations with their children about it. Find out what they want about their idols and remind them that you'll extend support but in moderation. Accompanying them in watching their idols' movies and concerts is also a good idea.