unfortunately, many (if not most) large commercial operations (where most of the honey available comes from) as well as many, many other operations treat routinely with terramicyn as a prophylactic treatement for AFB...this has at least two effects worth noting:
1. AFB is not detected by the beekeeper (or if it is, another treatment is administered) yet is present throughout the apiary. Anyone who says, "I tried not using TM, but got AFB...now I treat routinely" most likely has a "suppressed" AFB infection, and there are probably enough spores throughout the hive to cause a problem if the honey is fed to an untreated colony.
2. In such a situation, TM is likely used whenever symptoms are seen by the beekeeper. TM gets into the honey, and if the honey is fed to your hives, you are having some impact on the microflora that provides some defense against...AFB (whos spores are also present in the honey).
Aside from these issues, feeding honey is a not a problem. If you buy honey from the dollar store to feed your bees, i'd expect problems. If you buy honey from another beekeeper who does not have AFB, and does not treat with TM, there isn't much risk. Knowing where the honey actually comes from and under what conditions it is produced is the hard part.