Mobile advertising start-up X-tract has raised 3.5 million euros ($5.4 million) from Nordic VCs Creandum, who were joined by existing investor Eqvitec. The Helsinki-based firm says it has some 50 customers, including Nokia (NYSE: NOK), Telia Sonera and T-Mobile, who use their technology to hone their advertising on social networks. You can see the founders of the company pitching their company at a recent Mobile Monday event in this video posted on Alarm Clock.