Filtered Water is good. I also like to have a filter in my coffee maker to make sure no grounds get in my coffee but, it’s definitely not something I’d like Google to do to my website. It’s not definitive but, based on hard research it’s pretty safe to say that Google’s Penguin update is a filter looking for manipulative “anchor text” practices within backlinks. Even worse is a Penalty. This is completely different from being filtered because, in this case you get a physical letter telling you specifically why. A good example of this we see every Sunday during football season. The ref brings out the flag personally delivers it to the ground and points the finger at the person who committed the penalty. So if you haven’t been delivered your flag yet, it’s a good chance to avoid the filters.