Do you think putting reputations (star) discourages some users?

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I have a rating of 8 before, the few days ago when I reach my 500 posts, to goes up to 9. I was really happy, that time I appreciated the ratings. It encourages me to post more and more quality discussions. Yesterday, I have answered some discussions, a very few discussions, then when I opened mylot today, my rating go down again to 8. I am really discouraged now. I was working on a 10 star reputation and now I went back to where I started??? Do we have a right to know how these ratings are computed? Do you think these stars help mylot users?