Another important thing to note is that every time you post it takes your current karma and basically rates you twice with that current karma.
I.E. last time I checked I was at 3.11, meaning that I've made ~1100 posts at 3.11 karma, meaning that I've been rated 2200 times as 3.11.
Which is why when I tell people to go ahead and rate me down, I mean it. 2600 posts at 3.00+ karma means that they have very little chance in moving my karma unless they camp me for the next year.