Found an interesting blog post about Fanboyism and Brand Loyalty on forums, which goes into a little of the psychology behind some of the things we see mentioned here, such as justifying purchases.
In experiments at Baylor University where people were given Coke and Pepsi in unmarked cups and then hooked up to a brain scanner, the device clearly showed a certain number of them preferred Pepsi while tasting it.
When those people were told they were drinking Pepsi, a fraction of them, the ones who had enjoyed Coke all their lives, did something unexpected. The scanner showed their brains scrambling the pleasure signals, dampening them. They then told the experimenter afterward they had preferred Coke in the taste tests.
They lied, but in their subjective experiences of the situation, they didn’t. They really did feel like they preferred Coke after it was all over, and they altered their memories to match their emotions.
They had been branded somewhere in the past and were loyal to Coke. Even if they actually enjoyed Pepsi more, huge mental constructs prevented them from admitting it, even to themselves.
It's an interesting topic for me, as I have long had an interest in self-awareness and the things that affect my thinking. Directly relating to the topic though, I've long had a bias towards, say, Apple computers, but I'd say now I'm more aware of it and it doesn't block me from seeing the point of view of other people, such as people who are very proficient at building Windows PCs.
On Head-fi, there seems to be a considerable and arguably fanboy-driven "gear-fi" aspect to ownership, especially with portable rigs, leading to some criticism of the large amounts of money people invest into them, regardless of the relatively poor value of them (at least until such IEMs as the JH-13s came along). As well, concepts espoused in the Sound Science forum are not immune to this kind of things, as there are many fanboys that argue vehemently in some debates. The irony of that is, where some people are quick to point to ways that people can be fooled into thinking they can hear things that aren't there, they too forget that they are just as susceptible to fooling themselves in any of a myriad of ways and will happily manipulate facts, as fanboys do, to justify their opinions.