Instagram is now the babe of the social media scene for advertisers. And it's not hard to see why, because 13 percent of all people on Earth are on it, and 80 percent support brands. According to Forrester, loyalty – measured by user likes , shares and feedback – is also off-the-shelf, with a rate of 4.21 percent. That is ten times Facebook's, 54 times Pinterest's and 84 times Twitter's. But apart from such impressive topline numbers, challenges arise ...