... in http://connect.facebook.net/en_US/all.js
Props to @samvj for finding it. (he's sitting here and I said I'd submit)
if (!j.isEnvironment(j.ENVIRONMENTS.CANVAS) || !j.getClientID() || !l) return; if (Math.random() > 1 / l || m == '*' || ~ES5(m, 'indexOf', true, j.getClientID())) return; setTimeout(p, 30000);
where m is the blacklist.
Given that this function does nothing for 30 seconds anyway, it seems almost certain that it's a workaround for a technical issue.