Web 2.0 and UGC in Search

Explain this dichotomy:

Pharma often explicitly states “No advertising on user-generated content (UCG) pages”

However, search is 41% of the marketing spend. Have you seen search lately? The search engine results pages (SERPs) are full of UCG. Google just recently announced their search wiki, making it even more so.

I understand the rational/fears of adverse event reposting concerns, etc… but I’m not sure I understand why it’s “OK” on search, but no where else. Thoughts?