Twitter has posted about the usefulness and benefits of their Promoted Trends advertising products. In short they make the case that promoted Trends help lift brand messaging and create more positive brand advocates.
The primary reason behind that lift is, I think, this: The broader audience Promoted Trends reach means publishers are hitting more people who don’t already have strong opinions about the brand one way or the other. So whereas the normal audience may already be immune to the brand’s social media charms, reaching more people means reaching more people who have a genuine “Oh, cool!” reaction. That would account for almost everything else in Twitter’s findings.
It’s also worth nothing that this study looks almost entirely at engagement factors, not anything relating to actually moving the needle on sales. Some people might point to that as a sign of the weakness in making the connection between social media publishing and making the sale, but I don’t think that’s the case. Or at least it’s not the case any more than it usually is. Social media is partly about selling, yeah, but it’s even more about building up some positive sentiment and engaging with fans, customers and others and not necessarily about selling all the time.