I think this whole conversation is fascinating and I have been following along.
I did want to tell 50andstylish, however, that I think the information you got about J. Crew not offering larger sizes in a lot of catalogue items is actually a little bit off. I just received my new catalogue and looked through it to see how many items were available in only size 12 or smaller, and there were actually very few that fell into that category. The clothes that were available in only size 12 or smaller were:
A pair of very short shorts
A very short miniskirt
A pair of pants
I am guessing that they probably don't sell a lot of short shorts and miniskirts in the larger sizes, so they decided not to make them. The pants were a very slim cut, so perhaps those aren't big sellers in large sizes either?
And that's all I saw that wasn't available in the larger sizes. I did notice that a lot of the petites only came in sizes up to 12 petite, but they were available in larger sizes if you bought the regular. (And as a short person, I know that I wear a "smaller" size than someone of average height who is the same build as I am, so it might be that they don't have a lot of demand for petites above size 12 for that reason.)
I hope that makes you feel a little bit better about J. Crew. It really didn't look like they were excluding larger sizes when I looked at the catalogue!