I have no clever reply to most of your comment, but:

I personally do not submit more responses and posts because of the karma system.

In my case, it's very much a motivating factor. In fact, I do not think I would have ever been led to comment or post at all without karma. I think this is primarily because I consider it exceptionally valuable, easy-to-read instant feedback on how I'm being received, which I'm normally bad at discerning and find a very important component of any sort of interaction. I virtually never comment on other blogs at all.