While the US is heavily propagandised putting little merit on libel and legal falsehoods other countries are far more involved. The world is a big place with some legal jurisdictions more rigorous than others. Not all good but not all bad either.
Powerful anonymous libelous contributors that were producing heavily biased content would see the foundation itself being targeted for legal action. It might be slow in happening due to cognitave momentum and vanity but it happens. One thing that is an issue is that Wiki tends to play safe legally a bit too often.