Social media monitoring and marketing is a big business. There are tools that alert agencies to any critical posts for their brand/celebrity/product/keyword so they can defend or at the very least deflect any criticism with sock-puppet accounts. These accounts seem like normal individuals with lots of history but are either accounts sold to these agencies or home-grown to seem "organic".

Looking from outside people think karma and posts/comments count mean nothing but accounts with good standing, posts, comments has a big market in black hat marketing sites.