(S (S (BASENP (DT The) (JJ social) (NN network)) (VP (VBZ has) (VP (VBN been) (VP (VP (VBN used) (PP (IN in) (BASENP (DT the) (NN past)))) (PP (IN as) (NP (BASENP (DT an) (NN outlet)) (PP (IN for) (BASENP (JJ political) (NN expression))))))))) (PERIOD .))