Personally, I love anal. Giving, receiving, even in a vanilla context, I love it. For me, I wouldn't use it as a punishment, and I don't think it would work on me. The only way it could work on me as a punishment is to stretch me past my limits and until it hurts...and that's not punishment, that's just dangerous. I don't find it humiliating or shameful, so it wouldn't work from that angle either.

Should a sub offer it if it isn't their thing? I don't know...I guess it depends on the sub and the dom in question. But if it's not a limit, I don't see that it's a problem for the dom to expect anal from his/her sub.

Just my two cents worth