It may seem obvious to some, but the level it sucks at is surprisingly high, and causes some rather bad results.
Let's start with school; for reasons not entirely known to me, by about age 12 or 13 I'd already been labeled a "geek", in so much as I was "always right". Sure, I was probably the best in my year at maths, and not bad a physics, but quite how it all extrapolated I'll never know. Anyway, this led to someone always laughing if I answered a question wrong, which in turn meant by year 10 and 11 (age 15) I just didn't answer anything unless I was really sure. That kinda sucked. It also resulted in most of my shyness.
At collage (age 16 - 18 here in the UK), things were actually good; very little of the teacher asking questions, lots of just doing the work. Plus for various things, some people actually came to me for help.
(This is all going somewhere, promise.)
University (18 - 21) was even better, as there was entire groups of people with the same (and better) knowledge of things I'm interested in, and (probably much more importantly with regard to enjoying my time at Uni) people who liked me for being me, not because I knew the answer to something.
Since then (2 and a bit years), I've stayed in the IRC channel for the Computing Society (of which I was the webmaster for my time at Uni), and that has brought about another change. Firstly, I'll just say that IRC is probably the single worst way to have conversation, discussion, argument, whatever, with more than two people (it sucks pretty hard even for two people when it is an argument).
Anyway, one of the things that happens on IRC is the "mob effect", where one person says something that a lot of people disagree with, and they get mobbed. Often so much so that they simply don't get any chance to explain, defend or otherwise expand on their initial comment. The result of this is that I suspect a number of people, myself included, simply don't bother saying what they think sometimes, because they know that a) no one will actually listen, and b) they wont get a chance to explain anyway.
This has been exemplified over the past few days, as the IT people at Uni had some issues on Friday, and members of the IRC channel have been steadily decrementing their karma (karma works by saying Thing++ or Thing-- to show what you think of Thing), and although I don't want to defend what happened on Friday, I do object to a number of the reasons people have used for the decrementing, as well as the sheer volume of it, but I wont say anything because of the issues above.
Finally, to bring a Mozilla.org side to this whole story; I simply don't file bugs when things break here with my own builds any more, even though it is obvious that it's nothing to do with me. The reason: because certain people have (incorrectly) blamed things on the fact my builds are depend builds and other things relating to my setup. Either depend builds are fucking supported or they are not. My conclusion is that they are (unofficially only) most definately not, and that's simply because the entire build system is a pile of crap that breaks if you look at it funny.
And this is why peer presure is bad - it makes people keep things to themselves when they really shouldn't.