I'm not an Instagram user, probably because I'm too old to enjoy seeing my food in Sepia filter, mostly because I got my fill of that by watching the Wonder Years.
Big companies NEED to use social media as a customer service tool. Social media works best for carrying on a conversation, not for sales, so this isn't surprising.
Excellent piece out of the UK explaining a plausible version of why G+ exists. It's not a social network, and to think of it that way is to mislead yourself. The article suggests
Dan Zarrella loves to dissect vast numbers of social media posts to determine which language seems to be the most effective. His latest effort is summarized here: