Looks like Forever 21 has been taking some J Crew fitting rooms pics (slaps knee):
J Crew lace tee vs boxy lace overlay blouse - F21 knocked off the lace tee last year or the year before, spot on. This year they're knocking it off w/solid colored sleeves.
J Crew boatneck popover (review) vs essential striped rib knit top - The F21 top is much thinner & lightweight than the heftier J Crew top from last year.
J Crew crystal bow cuff (review) vs. F21's rhinestone bow cuff
J Crew Elodie stripe blouse vs F21's essential striped chiffon top
J Crew chiffon top (review) vs boxy button back top
J Crew striped sweater vs F21's boxy striped top - The top on the right is different, but the J Crew sweater is was first came to mind when I saw it.
J Crew silk boy shirt in windowpane (review) vs F21's grid pattern georgette shirt, grid pattern sweater and square print shirt - I like the one at the lower right w/the fainter grid.
J Crew sweater vs F21's striped georgette shirt - Sweater vs a top, but again I immediately thought of J Crew when I saw the F21 shirt.
There is lots of poly at Forever 21 right now and a lot of it is sheer. However, if you know how to shop F21 there there are some fun little tops to be had.