Does anyone follow-up on these types of social media smears or threats?

Ever since the election, sites such as Buzzfeed have featured lists of horrifying threats to the president’s life and racists rants (link NSFW) about his re-election. My question is, does the secret service or anyone else follow-up on this stuff – at least casually – to see if any of the threats are real or are these people just written off as fringe nut cases?