A quick look at popurls shows that of the top 20 sites featured on Furl, more than half are spam (unless there’s been a huge upswing in interest in colon cleansing and acne).
At first, the spam problem for things like Furl and Digg was about self-hype. "Hey," the poster says, "It only takes 30 people to ‘Digg this’ for me to see a huge traffic flow, so please, do it." But now, it’s a more focused and concerted effort.
Spammers are short-sighted and selfish, and don’t care what they wreck. It’s the enemy of anything open. Once again, just like with email and with comments, the answer is reputation. Get rid of anonymity or at the very least, track reputation over time. When reputable people speak up, it should count for more than when a stranger does. That’s the way it works in the real world, right?
[update: reputation, by the way, is not the same as a real-world ID card. It just means that your virtual identity benefits when you are consistent over time. Clark Kent has a reputation, even though he’s really… Superman.]