According to a study by comScore and ValueClick Media, the display ad placement strategy with the most brand lift is retargeting.
While display ads may once have been considered primarily a direct response vehicle, and many marketers still rely on measures of declining clickthrough rates as primary display metrics, studies have shown that banner ads provide an important branding vehicle and should be considered as such. Given the cost, reach and effect of various display campaigns, retargeting provides a large benefit with reasonable costs.
via Retargeting Used by Marketers for Cost-Effective Brand Lift – eMarketer.