eMarketer has published a study entitled “Social Commerce: Influencing Shoppers and Assisting sale” issued, which states that companies indeed use a social media strategy for brand building and need, but not to trigger active purchases via this channel.
For more information, see OnlineMarketing.de, the largest news portal about online marketing under http://onlinemarketing.de/news/haendler-nutzen-social-media-nicht-zum-verkaufen-sondern-zum-praesentieren?utm_source=feed&utm_medium=reader
The study of emarketer can be viewed here: http://www.emarketer.com/