In the real world, these social castles track not more than just click the button.
Because in fact, to really check the subscription you can not only everywhere(apicheck stupid there are no such), there is little you can do it.
And where you can check first on the website have authorization through the social network. I.e. In the case of several social networks necessary to drive the user to log in to EACH then to be able to check his podpisannoe. (I mean on the website to login via social. network, actually this possibility is not everywhere)