I first noticed this phenomenon back in the mid 90s between Sega and Nintendo fans. Those two companies were fighting it out to be the biggest 16-bit games console competitor. I also noticed that both sets of fans had a hardcore number who would defend the manufacturer of their beloved console, dismiss the other and would not listen to reason if their console manufacturer did something wrong or bad. It carried on into the 32-bit era with Sega vs Sony and then also Nintendo and also with Microsoft joining in the games market. That still continues on today, as seen in debates across discussion forums and video gaming comment sections.
I used to be one of them, I used to love Sega products and would not use anything else. That carried on until 2001 when Sega pulled out of console production after several years of bad decisions which damaged the company to the point of massive debt and potential financial ruin, if it wasn't for Sega's decision to go multiplatform and the $695.7 million private donation from Isao Okawa before his death.
But it's also appeared in a number of other genres and situations too. Football teams are the historic one. You get flame wars between Microsoft vs Apple vs Linux users, Gnome vs KDE, FM vs DAB and individual celebrities. Look at console releases or the release of an item from the next company I'm going to talk about, people queuing for days to be the first to own a newly released item, high fives, applauding and celebration of consumerism. I never got the point of it myself, I'd rather just get something as and when, I've never been one to follow the herd mentality ever since 2001.
Apple is a company which has a passionate core of supporters surrounding it, and has been the centre of many a documentary in its time, but it is starting to grow it's own religious cult of hardcore supporters, for whom Apple is the only way and anything else is sacrilege. I think Apple understands this dedication to their brand and price accordingly - it really is the case that some people will pay anything to own an Apple product. This dedication also creates a backlash and negative perspective from other people, whom mock and even go to lengths of destroying Apple products because they despise the religious like dedication of Apple supporters.
But it's also appearing with celebrities on Twitter. Justin Bieber is the prime example but it's also apparent with One Direction, Lady GaGa and other accounts. Regular trending topics start about the celebrity, usually from people whose own account pays homage to the said celebrity. Anyone who dares criticise or point out fault with the celebrity is dismissed out of hand as a "hater". And as with Apple, it has developed a counteracting group of people who detest the religious like following that people have for a celebrity.
My view on it from past experience is that people should like and follow things, but as with so much in life, restraint, realism and the middle ground is where you should be at, don't dismiss other things or people either.