I agree with you entirely jolly_roger but I would add that having scammers on their sites increases their numbers without providing anyone with a financial benefit, but posing a risk to those who might be of economic benefit to advertisers.
Quite simply those sites that don't take positive action to exclude scammers, or who actually make members details available to scammers should be shunned. Our site moderators aren't Gods (they may disagree

) who have special psychic powers, but scammers who come here are removed speedily and methodically. It's not an impossible task by far.
I'm not actually saying anything revolutionary, but merely stating the obvious, that it's unsafe to give your personal details to a site that doesn't treat them securely, and who don't take action to exclude scammers. It's for the benefit of the sites too, as a site consisting merely of scammers has no worth to anyone.
... and I didn't even mention ad sites.