It all depends on what is being AAd and what its use is going to be.
A game sprite that moves is not AAd to the outside generally whereas a still image usually is. The moving sprite usually has BG changes so one never knows what needs AA.
Blurring when it happens, is when you AA anything on both sides, over AA or AA poorly.
There is also the option to SelOut in certain situations which is not AAing but serves the same function.

Oh you kids and your new techniques 

@DB, we should copy that to the noobtorial and even cure's thread. Don't delete from your host just yet.
Does anyone need credit for that? Did you make that?

Thanks,everyone.

The Selective AA looks a bit like selout,I think?

I used to create sprite without outlines, and use shades and shadows in some places to serve as outlines. In that case,does it need AA?

Sometimes I finish the picture in a larger scale to have a "smooth" feeling,and AA seems less important in that case since the sprite is much bigger and dose not have an outline.

Nothing really NEEDS AA.. it's really up to the artist. These are just techniques that produce certain effects, and it's up to you if you want them. It's just that people can become conditioned to expecting certain results and qualities and may think those are needed.