I seen this ad on Craplist...?

If she's very old or otherwise unfit for use, its not unusual for someone to give her away. Maybe she costs a lot in the way of feed or vet bills. Maybe she's not trained AND old and they think no one will pay good money for her. Maybe she's the "least valuable" to them for whatever reason and she's the one they decided to get rid of. I personally don't think it's right to give away any animal you've taken on. You SHOULD give a horse a home for as long as you can care for it properly. If they have to get rid of her, its a shame they are giving her away. If they don't really do their homework and find someone who really wants an old, "frisky," costly horse she'll probably be on the first truck to Mexico for the price of her meat.