Whenever you work with other people long enough, you'll no doubt encounter elitism. This is a given since it is a part of Human nature. However, not all elitism is bad, and its important to be able to recognise the difference.
Some elitists get more work done and are better at their jobs than others. But then you also have the elitists who are just making life hell for other people and only do as much work as they have to because their view their own creations as "perfect".
When we talk about "good" elitism, we have to understand why it is beneficial to getting stuff done. A person with a bit of an ego, who has a bit of pride and is a bit headstrong is a lot less likely to become distracted, dissuaded or even depressed by obstacles.
This is obviously because they believe their own abilities can overcome it, and usually they are right. But they rarely allow this attitude to cause problems for others; merely appearing as slightly full of themselves and little more. This is the kind of elitist that you want to have on your team.
And then you have the "bad" elitism. There are no words that can truly describe how awful these people are to work with. If you've ever fixed some bug in a major application framework such as GTK+ and submitted a bug report with a full patch, you will probably understand what I am talking about when the response is "can't reproduce, works for me, won't fix" while the developer behind the bug tracker completely ignores the fact that you wrote a patch.
But that's not all. It gets even worse from here, because some developers even go as far as to become offended that you submitted a bug report for their perfect creation. They become rude and aggressive, and demand that you stop saying that something is wrong with it. If its a forum, you may even get banned.
While this is obviously a problem in any line of work, it is a particularly bad problem in open source projects where the developers don't get paid. These kinds of people feel like doing their job is a courtesy to others and that their work is perfect and throw massive temper-tantrums when it is being "insulted".
Furthermore when entire teams (or worse, companies) are made up of bad elitists, it can become completely impossible to reach them or come to an agreement with them on any issue, causing once-promising projects to spiral downhill indefinitely despite others' best efforts to intervene. We've all seen it too many times.
Unfortunately, being Human beings, we are prone to mood swings, and that's where the "ugly" elitists come from. The people who seem to oscillate between "good" and "bad" depending on which side of the bed they woke up on. One day your star developer might be friendly to all of his coworkers, acknowledging all of their efforts while being oh-so-slightly full of himself, the next day he might be screaming at them because their work is so terrible they are slowing him down and should just get fired already.
The problem is, this trait is often found in some of the most talented artists in the world. Its an old running joke that someone who is intelligent and creative also has be somewhat unstable. But what can you do when they are the best?