martinibuster - 2:55 pm on Feb 21, 2013 (gmt 0)
Google prefers to use scalable methods for determining whether a link will pass full, partial or no PageRank. In addition to on-page factors such as relevance of surrounding text, context of the web page, location of the link within the web page, there are other factors such as inbound link quality to the site and links to the article itself that lend authority for one thing (your site topic) or else do another (depreciation of PageRank due to general/fuzzy/off-topic to outright low quality inbound links to the site/page where your link is placed). These are all calculations for determining how much (real, non-toolbar) PageRank to flow to the linked site. This is not to be confused with algorithmic considerations for ranking the web page itself, in this case the press release.
These PageRank flow considerations are pretty much the same whether the site is a directory, a paid link, a viral link campaign link, a link on a widget, a link on a duplicate content article or a press release. It's not that the link is coming from a press release site that is the issue. It's all the other considerations I described above that are at issue.
So while some people will declare that article marketing is dead, that viral links can never be penalized, that infographics are going to be depreciated, you can see from what I posted above that a scalable solution for depreciating links is preferable because it will cut across all link types and contexts (viral, infographic, press release) and assign it a value for how much PageRank (or not) to flow.
For a real example (something happening right now), even in a case where the toolbar is fooled by links obtained by hacking high PR sites so that the toolbar displays PR 8 or PR 9, the algorithm cuts through the noise and won't rank it, despite what the toolbar shows. The cheating site with the high toolbar PR does not rank for anything because the algorithm isn't passing internal PageRank and isn't ranking it where it wants to be.
This ability or inability to rank should thus be a signal of quality for publishers who are wondering whether a site is worth obtaining a link from. Everytime I posit this notion, one or two link sellers chime in with self-aggrandizing denials. But think about the scalable methods described above and make up your own mind.