I'm not a pro, nor do I currently endeavor to sell my images (though I do have a few half decent shots posted online) and I suppose it's fair to say I'm not particularly paranoid about finding them used without permission. I wouldn't be exactly thrilled, either.
I'm really not a fan of watermarks or signatures, though I do appreciate the branding aspect. A service like Digimarc is more appealing, as far as security is concerned.
Should I be anxious about putting my images online without watermarks?
Apologies if this subject has been flogged to death; a search failed to satisfy my curiosity.