A) Horse is very nice tasting; more taste than beef, though sometimes a bit strong for my taste. Supermarket beef -> supermarket horse -> real beef -> real horse in order of "having more flavour".
B) Mixing horse in with beef is a problem because, on one hand, some religions don't eat horse and, on the other hand, in some countries horses aren't eaten as regularly (like rabbits, or snails, or frogs. I love all of them! We belgians eat whatever meat we can get our hands on
)
C) The *main* problem besides that, is that the horse meat in question comes from horses declared "unfit for human consumption". For a variety of reasons, these horses weren't allowed to be packaged and sold as horse meat (which is actually
more expensive than beef in Belgium, so go figure). Too much antibiotics, wrong feed, animals too old, whatever. It was supposed to go to beef feed supplements (I still think it's freaky that almost all industrial cattle and chicken feeds contain chicken, cow and horse meat - we're turning herbivores into omnivores).