A new report out today from eMarkerter shows that 32 percent of online retailers have a presence on Facebook as compared to 27 percent on MySpace, making it the largest social network for online retailers. The findings suggest not only that Facebook is popular among online retailers but that social networks in general appear to be a promotional channel leveraged by a large portion of these companies.

One thing the report didn’t answer was how many retailers were polled. Additionally, one would expect online retailers to be quicker to leverage new technologies for promotional purposes. It would be interesting to know what percentage of offline retailers have a presence on Facebook or other social networks. According to a study published by Rosetta, of the top 100 online retailers, 59 had a Facebook fan page in September.

Have these new pages resulted in an increase in revenue? Unfortunately there’s no way to know as that information wasn’t provided in the study. It would have been great if this study provided more information but eMarkerter studies tend to be a bit sub-par in terms of the breadth of their findings. It will be interesting though to see how online retailer and offline retailer presence on fan pages shifts over the coming months.