Oh i hate this kind of people! Manipulative, lazy, selfish, irresponsible people can really piss me off. Normally this kind of people are quite smart, because they know how to manipulate one's mind and make people work for them, so that they can sit back and relax and in the end of the day, they get the credit. Or they use all sorts of poor me stories to hit your soft spot and get your help.
When we encounter this kind of people in life, before we help them, we should examine this person and skillfully correct them. At this point, i do agree with Big Uncle, harmony is the key in team work. Fightings, conflicts, backstabbing are not the substance lead you to success. Give and take, forgive and forget.