Personally speaking, I won't buy corals attached to frag plugs. That pretty much means that I won't buy frags from the "Frag Farmers" on the web.
I do buy frags that are glued to natural reef rocks, or more mature colonies that aren't attached to a plug or rock.
Hopefully there will be enough reefers voicing their objections to little round ceramic disks that frag farmers will get the message and stop using them. But that could take a long while.