I was under the impression there could be only one omega male in a pack and that it actually serves a purpose - having a whipping boy helps social cohesion apparently.
Anyway, the top reply was pretty amusing.
It was entertaining to read both the article and comments here; very illuminating! What I see is something like this. A intelligent, educated woman who is probably not super attractive has built up a little bit of bitterness against men. She then writes an article documenting the pop cultural trend of useless "omega males" being celebrated by Apatow-esque comedies. A bunch of male Slate readers who probably don't make too much money felt that the various "Omega Man" descriptions by the author hit a little too close to home and responded.
What men and women both need to realize is that both groups objectify each other constantly. Men see women as "hot chicks", "fat chicks", etc., with various subdivisions among the groups. Women view men as "alpha males" "omega males", "sad beer guys", "mimbos" etc.
As a young man who grew up in the 90's and went to a liberal arts college I do think it's ridiculous for feminist-leaning women to complain about "Don Draper" type, alpha-male oppressors in the 60's, indoctrinate men for several generations to act more like "omega males" and then complain when after a couple of decades there are a few less Don Draper's around!