PR also makes it into Wikipedia through sanctioned channels -- namely mass media citations which are considered "reliable sources", even though the content of the citation comes from a press release or helpful PR person.
This brings up an issue related to Wikipedia's policy that requires substantial third-party coverage for new articles. It is a flawed test for the importance of a subject.
Press coverage tends toward the sensational, visual, beautiful, controversial, current, language-specific, and easily explained. If a topic doesn't meet those criteria, it probably won't be covered by the press -- unless the topic in question has some well-connected PR firm or publicist pushing for it.
Another issue with press coverage is "established" media is contracting. There aren't as many editors assigning stories, or reporters crafting unbiased profiles of companies, organizations, topics and people. This has an significant, indirect impact on the types of topics that can be sourced according to Wikipedia's official rules.
1. http://news.cnet.com/8301-1023_3-57514677-93/corruption-in-w...