As far as protest leaders go, they meant the people on the maidan from a year or so ago - i.e. Ukranians protesting against Putin's puppet Yanukovich. As for why they prefer VKontakte to Facebook? No idea as I don't use either, but I'm sure there are "reasons".
Durov just has the potential to raise all sorts of hell if he should like to - I don't personally think he has that information, and it this point, the accounts in question have probably long since been deleted. It's more of political in nature than actual hard data that can be gleaned from him. The original article in summary goes into a little more detail on that aspect.