Someone posted a link to
https://secure.wikimedia.org/wikipedia/commons/wiki/Category:Hogtie_bondage
Delving further, we find https://secure.wikimedia.org/wikipedia/commons/wiki/Main_Page says Welcome to Wikimedia Commons, when in fact the real site is http://commons.wikimedia.org/wiki/Main_Page . Or is it?
In fact on any page on either site, one cannot find any link to the corresponding page on the other site.
So now everybody will be passing around two times the amount of links to what in fact is the same material.
OK, I found the pattern for converting one to the other: https://secure.wikimedia.org/wikipedia/commons/wiki/Category:Hogtie_bondage _________________ http://commons.wikimedia.org/wiki/Category:Hogtie_bondage
One would hope the owners of Wiki[pm]would redirect etc. one to the other, to stem the proliferation of non-canonical links.