From what I can tell it isn't the norm or the majority, but I have recently seen a few agents reference wanting to see platform even from queriers of fiction. Those agents aren't for me.

There've also been a couple of agents I've determined wouldn't be for me to query based on tweets--things not referenced on their agency websites--and others I might not query had I not seen their posts on Twitter. IOW, social media can be a helpful tool like any other, for queriers, agents, and editors.