Originally Posted by timski

I suspect that's going to annoy a lot of long-time players, who feel the need to go back and do something that is now trivially easy, just to prove their history. Of course some things remain genuinely hard, regardless of when they were accomplished. So I think Blizzard need to be careful there isn't a backlash among players who feel cheated by not having former achievements recognised.

Some achievements are linked to items, so should be easy to retrospectively award.