The funny thing of on-line direct debits in the Netherlands is that they are legally/formally not allowed given that a written signature is required from the customer (who needs to send in a signed fax or form). If this signature is not available, the company may not use the direct debit mechanisms.
Despite the formal regulation, the reality is different. The Sponsorloterij (a lottery) for example allows customers to order lottery tickets and fill in a direct debit form on the web. Then, if some-one mistypes his account number on the web into your account number and you als a legitimate client try to undo the lottery direct debit that popped up on your account, it is impossible (all bank employees know that reversing a direct debit for lotteries is forbidden).
The sponsorloterij is one of the many experiences with the illegal online debit. Undoubtedly more will follow.