Why "top posting" sucks.

A: Because it reverses the logical flow of the discussion, making it difficult to follow.
Q: Why shoudn't I top post?
A: No.
Q: Should I top post?

Alternately:

A: Yes.
> Q: Are you sure?
> > A: Because it reverses the logical flow of conversation.
> > > Q: Why is top posting frowned upon?