I don't know if the from_behind tag has been discussed or not, but it's a tag that's been bothering me lately. It seems that most users of the tag implement it mostly for sex done in the rear, rather than the angle which the subject is being viewed at in a picture (such as the from_above and from_below tags). I've changed the wiki article to be more neutral and anatomical, but I'd like to hear what the community has to say.
Updated by r0d3n7z