Once you've paid for an order it isn't your money any more (they're presumably not operating or licensed as a bank). In your clothing example your only recourse would be to sue the clothing store for failing to deliver your clothes (breach of contract or the like). In theory you could do the same thing with Silk Road, but the site operators being anonymous makes that rather difficult.

(Of course in practice what you'd do is a credit card chargeback - but bitcoin is specifically designed to make that impossible. If you choose to send an irreversible "currency" to an anonymous recipient, frankly you deserve what you get)