You clearly have never seen the OTRS queue if you think Seigenthaler is the closest to a suit. There have been over a handful of cases (against the WMF or Wikipedia editors themselves) and some even received media coverage, though Bauer [1] is the one that comes to mind at the moment but it certainly isn't the only one. [2]

[1] http://arstechnica.com/tech-policy/news/2008/05/dumb-idea-su...

[2] http://www.citmedialaw.org/threats/american-academy-anti-agi...