Do guest ever come in and say "hey, I saw so-and-so's post on Instagram and now I want a bottle of whatchamacallit!"? If so, what are they asking for? And who are those "influencers" who are inspiring them to drink more of Brand X or region Y?
I would say that Social absolutely moves certain bottles. The evidence is clear as day. I could make a pretty long list of examples, but I'll keep it short... Overnoy.
While I would never ask a Sommelier if they a had bottle that I had seen on social media (that just seems tacky), I do keep an eye out for bottles at restaurants that I have seen on Social but have not had a chance to try. Often times it is the only way to try these wines at somewhat reasonable prices.
Agree it moves bottles, but in no way would asking a Sommelier about a bottle you saw on social be tacky. It's 2019. It's main stream now. It's the world we live in, not tacky.