Social media marketing spending in the European Union (EU) will rise over the next five years, boosted by increasing numbers of addressable devices; consumers' willingness to use them; continued consolidation of the social network landscape in Europe; and growth in the number of Western Europeans who use social networks. The main factors likely to constrain growth in spending are upcoming EU-wide legislation governing online privacy; consumers' wariness about their data being held by social networks; and marketers' difficulties in understanding the return on investment (ROI) of spending on social media marketing.