I suspect there is a new type of link in play. A social link. A fleeting mention with no permanent link but gather enough of these, from NON automated accounts and from different people, and they carry the same weight as links.
Interesting thoughts. In the local search area, it's being widely acknowledged that unlinked "citations" in a
trusted local directory, are a factor in map and 7-pack rankings, though not in organic.
(See more about local citations in David Mihm's 2010 Local Search Ranking Factors discussion... [davidmihm.com...] ) Local citations, though, need to mention the company name, location, etc, and to be listed in a trusted source... like a local directory of known quality. For a social mention in non-local organic to be useful as something like a citation, I assume that, at the least, the company name and a product or service would need to be mentioned together in a relevant and trusted setting, so Google can extract the semantic information from its data and have some faith in it.
Whether these social mentions carry the "same weight as links", at least individually, is debatable. I'd argue that, if they exist, they don't carry the same weight. Cumulatively though they may be an important factor that could affecting branding, eg, which is then somehow folded into organic.
Buzz is built on this, it would make sense that pagerank incorporates it too. Being mentioned by someone new does indeed carry value but since the future effect of such mentions is hard to place a value on I'm guessing the act itself carries a value.
Many aspects of the Google algo are trying to come up with a computerized weighting for web equivalents of human perception and behavior... and it makes sense that Google would want to do this with "buzz" too. If there is an algorithmic measure of buzz, it ought to behave like buzz, perhaps being time sensitive and rising and falling with the noise level. There'd be a question, I'd think, about how to sort out long term reputation from short term buzz.
it would make sense that pagerank incorporates it too.
I wouldn't say that "PageRank" incorporates this. PageRank is its own well-defined, patented and trademarked entity... but it would make sense to say that the Google "algorithm" might incorporate social and buzz factors. Keep in mind that social mentions are easily spammed, so Google is probably looking for ways to build social reputations and to use them to assign weight to the social citations. This is more easily done in a personalized search context than in just plain vanilla search.
The question of nofollow links brings up a lot of side issues... and I don't think that nofollowed links are simply being followed and they're not telling us. It's possible though, that, in the proper form and context, which would need to go just beyond keyword anchor text, nofollow citations might also be a factor in this kind of hypothetical social algorithm.
There have been discussions on WebmasterWorld about how effective social traffic is. Whether or not there is a direct algorithmic factor, social buzz, at the least, leads to traffic which might lead to long lasting links which can carry weight or trust.