I think it's more reasonable to assume that
Wikipedia (which shares many features with Google,
Yahoo, Twitter,
Facebook and other social networks) has been the subject of this kind
of demand than that it hasn't. No one with direct knowledge would be
able to do anything other than deny it, but we can easily see why data
held by Wikipedia (including partially anonymized e-mails, file
uploads, talk page communication, etc.) would be of interest to
intelligence agencies.
The capacity of the Wikimedia Foundation to keep a secret of this nature
is law. Simply too many outlaws; something NSA could probably figure out;
they are not called intelligence for nothing.
Fred