Google PageRank is sooooo.... how to put this politely... stupid. We need a high page rank in order to make money with our web sites, but unless you are using one of the methods that Google allows they will slam you page rank, marking you as a "bad neighborhood". They don't allow you to sell links to other sites. This means no paid articles, no back links, no links to advertisers at all, unless you use rel="nofollow".
What if you mistype the nofollow link? Forget to add it? What if you create a blog roll of all your favorite sites? All these things can cause Google to tag you. Is it fair for them to tag you as a bad neighborhood because you choose to sell links on your site? How does that damage the system? I've done several Google searches on how this can damage the system and all I can find is a lame excuse that it alters the search results. Basically, those that can pay to have their name out there would rank higher in the results than those that don't.
All right, I can understand how that might be a bad thing, but let's consider it for a moment. Isn't buying advertising normal? Isn't that how businesses have built up their businesses? We all know Sony, Pepsi, Ford, Microsoft, etc. Why? Because they make better products than others? No, it is because they advertise better. Just because Google made it without advertising, does not mean that it is not a normal part of the world.
Even without allowing the links, those that can afford it are going to rank higher than those, like me, that can't. If you can afford the time, or to pay someone for their time, you can get millions of links in short order. Links that you don't have to pay for. Paid links are just a easier way of doing the same thing.
It also makes it very hard for those of us trying to make a little extra income to make it. We have to be so careful of how we allow advertisers to use our space of we loose our rank. All right, maybe I'm just bitter over having lost my rank on one of my sites, but it is frustrating. I worked hard on that site, trying to make a few bucks. I have a few users who enjoy it and come back regularly. It is doing all right. But Google comes along and decides that the links that I have (yes, some, but not all, were paid links) make me a bad neighborhood. I loose my rank and along with it some money I was earning off a few links. (with no PR, they no longer want to link to me).