As Ed noted, and as also noted in another BB 3D thread, the on-line division of BB do have some 3D Bluray titles for rent. I've personally rented roughly 10 or so. These are true 3D Blurays, although their selection can be a bit odd at times.
GRAND CANYON ADVENTURE
ULTIMATE WAVE TAHITI
MUMMIES, SECRETS OF THE PHARAOHS
JOURNEY INTO AMAZING CAVES
KENNY CHESNEY SUMMER IN 3D
Plus a couple of Dino IMAX titles that escape me at the moment.
There are some 3D BluRay titles that have been listed for months, but if you are a member, they show up as unavailable once you select them. (JOURNEY OF MAN, SEA REX, PIRANHA etc etc) This is a bad ongoing Blockbuster issue with a number of their 2D titles as well.