It may be getting harder for Facebook to stand out among other social sites for ad revenue, given the increasingly crowded space, but_Adobe's latest social media intelligence report for the first quarter of 2014 found that revenue referred from most social channels to retail sites dropped quarter-over-quarter, except for Facebook. Facebook's referred revenue per visit rose 2 percent quarter-over-quarter, while Twitter and Tumblr's figure_declined by 23 percent and 36 percent respectively. Year-over-year though, Tumblr's referred revenue per visit was up 55 percent, followed by Facebook at 11 percent and Twitter at 5 percent.