Tagworld, the teen social networking service, raised $7.5m from Draper Fisher Jurvetson and won itself a mention in Techcrunch as the next generation Myspace competitor. One would be excused for thinking that's all one needs to succeed these days. But something's up with Tagworld. Its active user base, dwarfed by Myspace and Facebook, is declining. And the company's suffered a series of executive departures. Anyone have the scoop? Update: HipMojo.com has an explanation.