As long as inbound links influence ranks, they can and will be manipulated...it forces people into Adwords.
Google is such a bunch of asshats. When I hear non SEO-types out there talking about Google, you'd think it was a non-profit, benevolent group that just wants to bring you the best search results possible. But it's a business with share holders that it has to please. That's why there's these continual shuffles, to force people into buying ads from google (can we all just go to Bing?), as the person mentioned above. I believe that they also want to force people into using youtube and blogspot, because those pages are so easily ranked.
But Google will never be able to totally discount "spam" aka blog posts, blog comments, form posts, profiles, yahoo answers, etc. They cannot totally discount other people's "recommendations." They must take these into consideration because it's a very valuable way to gauge what people want to see, since most social media interaction is legit. Other metrics available (domain age, edu links, etc) do not even come close to the power of these online conversations.
They already do have a system in place for discriminating against shitty links, and it's called PR. I think that google is going to continue penalizing high OBL, etc. And that the system has not drastically changed. If it has, well, they are going to have a lot of pissed off Scrapebox owners with spare time to blast everything to kingdom come and the King of the North shall rise! And they'll have to readjust.
Just remember, google hires the best of the best and really understands human psychology, especially the power of fear.
