Shame your non-paying clients in public

Might be a way to encourage them to pay you, but to your prospective clients who don't know the backstory behind nonpayment, you will seem petty and vindictive. Maybe you didn't deliver as promised, or the bill just slipped through the cracks by accident by ending up in the engineering department instead of accounts payable.

The facebook/twitter route is a public record, not only for the client but for you.

Do what's right for you, not what's wrong for them.