People can give you positive and negative reputation based on what you post. If they like it, they will probably give you positive reputation. It they don't, you'll get negatives sometimes. Sometimes you may not get any at all. You can do the same to other people 10 times a day. Its that little button under your name with the check and the X.
Thats great, now we can keep a tab on those negative post people who no matter how optomistic a fan is on this board have to come in and rain on everybodys parade and call it there opinion.