When Social Media studies report likelihood of purchase ...
This is a study from CMB, http://goo.gl/SsQZc
, that found
"The real question on our minds was does engaging with consumers via social media sites like Facebook and Twitter make consumers more likely to buy or recommend the brands they follow? 51% of Facebook fans and 67 percent of Twitter followers reported they are more likely to buy that brand since becoming a fan or follower."
First this is a stated preference survey not based on actual behavior. You can't read anything into this report.
Let us take this as true. What the study says is
P(Customer | Fan) = 0.51
In the previous paragraph it says, P(Fan | Customer ) = 0.49
P(Customer | Fan) = P(Fan | Customer) X P(Customer) / P(Fan)
So what this means is,
P(Customer) (probability that a person is a customer) is almost same as the probability they are a fan P(Fan)
In other words, anyone who is a fan is likely a customer as well and vice versa. What CMB should say is, don't bother.