A chief marketer survey allowing various online marketers to pick multiple ROI tracking metrics for their social media campaigns came up with the following findings:
60% of Marketers polled said they will measure ROI by number of followers/friends/likes generated by that particular campaign.
39% vowed to measure ROI by sharing/forwarding/re-tweeting or sharing brand content that the users indulged in.
35% correlated ROI to generating qualified leads from social media marketing efforts.
30% benchmarked it to time spent or visits generated, in engaging with the branded content.
25% marketers were comfortable with ROI calculation which measured sales generated through the channel 18% mapped Social Media ROI to brand favorability as measured by various surveys.
Main charm of any non standard ROI calculation metric is, that it is never falsifiable. You can take one or the other angle, to always justify the ROI generated.,
Karl Popper in defining a scientific theory said that for a theory to be scientifically valid, there should exist certain conditions under which it is logically falsifiable. If not, the theory can never be disproved or by inversion, proved.
Same is the quandary for Social Media ROI. Unless you have situations where you can clearly state that ROI was not created, you can always prove that it was created though it cannot be accurately measured.