Custard pitched against two other agencies for the business, which will involve positioning realbuzz.com as a 'complementary' website rather than a competitor to social networking giants Facebook and Bebo.
'We aim to prove that social networking isn't just about ego building,' said Custard consumer director Stu Campbell, who will lead the account team.
'It will be interesting to see how the big players view us as we're not aggressively taking them on or trying to steal users.'
Custard's other accounts include Toshiba, AMD and instant messenger ICQ.