When did brands start thinking that sticking a Facebook or Twitter logo in their advertising without any context on how to actually find them there was acceptable? You'd never see a brand simply post a stock image meant to represent a "website" and expect people to instantly know the URL, so why is social media any different? Maybe the Microsofts and JetBlues of the world can get away with this, but being a Fortune 100 brand doesn't mean customers will instantly know your username. (Coke? Coca Cola? Coca-Cola?)
I'm a firm believer that any brand engaging in social media must be all-in and show customers that it's an important part of their communications mix by promoting their account anywhere they promote other digital properties. Simply placing a social networking site's logo on one's advertisements and expecting their customers to do the work in proactively searching for their page is lazy and stupid, especially in this world of spoof accounts and unofficial fan pages.
We're quickly approaching a time when not having a presence on any social sites will make a brand seem as out of touch with their audience as not having a website looks today. Customers are so used to seeing a Facebook logo on everything from beer bottles to yogurt cups that it lacks any sort of impact anymore. If a brand is going to use it in their ads, at least make it useful to us.