I think one can argue with Wikipedia's statement that "we only host your content". If Wikipedia empowers editors with administrative privileges, including the ability to enforce rules like "no original research", lock and delete articles, block users, etc., they would seem to wield a lot of indirect power over what kind of content users can and can't post.

Contrast this with a web hosting provider like Rackspace or Amazon AWS who really "only hosts your content". They generally won't delete your content unless there are legal issues (e.g., alleged copyright infringement, court order, etc.).