Why my answers are deleted???

First, don't feel bad for something that's out of your control. Some posters tend to ignore or forget their questions after they posted it, so the system will automatically remove the questions after they expired -- the posters get point-deduction from their Knowledge+ accounts, but like they really care if they chose not to read the answers provided.
I ran into the same situation couple months ago. The system said the poster removed the question manually. I asked the poster if there's anythng wrong with my answer so I can improve it in the future, he said my answer is fine but he just doesn't know the buttons very well and picked "Remove" instead of "Best Answer". Ya, some of them are idiots
Another situation, some posters are just jerks. A poster asked for factual answers, like "How many horsepower are there for a GT-R", I provided the answer. The poster removed the question, I asked him why and he said "I don't like your answer". I asked him which part of my answer he doesn't like as it's just a fact. He said "I don't like is I don't like, I don't have to tell you why". Ya, you can't please everybody in the world, and you don't have to if that person happened to be a moron.
So, sometimes it's not the system's fault. And don't get upset about it.

2009-03-30 11:29:25 補充：
When the poster removes the question by himself, no extra points will be deducted (as penalty) from their account, as this action is not considered "Ignoring the question".

never mind , just time-spending game !!!
"score" not money