From various threads it appears that the PRs of a number of sites have recently dropped. A typical example might be from PR6 to PR4. Some people seem to be calling this a penalty. But it seems to me that a penalty would cause the PR to drop all the way to zero. A drop from PR6 to PR4 could just be a readjustment in the value that Google places on different types of links, such as a discounting of purchased links. That's not a penalty. Instead it's just a way to prevent some sites from gaining an unfair advantage by buying links.
It all depends on what you define penalty to be. It is a penalty because Google decided that millions of links in millions of websites are useless. They did not drop it to zero because some links are natural
I think this is what (with respect) is called a duplicate Thread With no value as Thread after Thread here has the same topic Are you following the category Thread trends or are you just opening a new Thread as Link Bait Personally I think you are the latter