This image was lost some time after publication.

It's not Ning's porn-sharing communities, Facebook's co-ed antics, and MySpace's ninja sex angel users that prevent these social networking sites from making as much money off ads as hoped. It's the issue of getting quality attention with each insertion, writes Bryant Urstadt for the MIT Technology Review. He doesn't blame the "rude content" (you know, what the users do) or the advertisers getting skittish about running a banner adjacent to the list of people you've slept with. It's not users being naughty that's the problem — it's that no one knows how to sell against "bad behavior" yet.

An enormous, highly visible brand may not want to risk seeing its ad wind up on a page such as that run by the actual Facebook group "I've Had Sex with Someone on Facebook," which at press time had 59,353 members. Or consider the MySpace profile (turned up after about two minutes on the site) of 18-year-old "Nikki AKA Death Angel!," which is adorned with the motto "Don't fuckin fuck with ninjette bitch we'll cut ur fuckin head off an give it to ur momma."

When spending the majority of their time browsing content like this (or, more likely, content like this slightly more relevant to their friends), what are users thinking about? Checking out an ex's profile, we're more likely to remember the photos of the new sweetie, and not the "Last Minute Cabo Deals!" enticement next to it. If anything, that's salt in the wound. This new argument goes, if advertisers could sell based on users' messy passions, we users will stop playing Scrabulous — or dreaming of getting back together — and pay up. Sex does still sell.