I attribute the the practice of continuously complaining to either insecurity, lack of respect for others, or a deep pain or conflict. I have to admit that it is indeed a struggle to maintain a conversation with someone who can only complain and point fingers. It is simply easier to carry on a conversation with a person who is communication in an open and positive manner, even if you disagree with them on a topic. I consider it a character flaw, but this is only a personal opinion that I hold. I am quite certain that I have character flaws as well; we all do.
People who complain a lot usually are self absorbed and haven't taken the time to observe their part in the problem they are complaining about, which by the way seems to rampant on the poll site. Not having a very sophisticated world view is one's own responsibility and a person should own it.