[fnurt]

It really, really depends on a lot of things, like where the raise is coming from, whether the raiser is short-stacked, and what type of player is involved. AJ is a tricky hand; in some situations it would be a no-brainer to defend your blind, and in other situations it would be crazy.

If the raise is not coming from a steal position, and the stacks are fairly normal, I normally wouldn't defend with AJ. On the other hand, if the raiser has been stealing a lot and you can put him on a wider range, it's fine to play back at him. This is one reason why you need to keep a close eye on your table and see who is raising more than normal.