This looks like an Echinobivia (XEchinobivia 'Rainbow Bursts') or Sea-Urchin Cactus (Echinopsis oxygona). I'm guessing this plant came from Altman Plants, and they are notoriously bad at labeling their plants correctly.

The member who added this image has not been around for a couple of years, so I think we will be on our own sorting this out.

@mcvansoest do you have any ideas?

It certainly would appear to be something else. Not sure what it would be, but E. tarijensis is a lot spinier:

http://www.agaveville.org/view...

Maybe the generic Echinopsis entry is the right place, then.