If Banks have the capacity to check your account balance for sufficient funds prior to letting you withdraw money from an ATM, why don’t they use the same technology to check your account balance for sufficient funds prior to accepting an automated debit request? Technically speaking, it wouldn’t be that difficult — it just requires a little will.
Unfortunately they don’t appear to have the will. The cynic in me thinks that it’s so they can charge you a $30 dishonour fee — but come on, it’s Banks we’re talking about here, they wouldn’t do something like that…