Fuck if I know. I haven’t done any exhaustive research. I don’t have published books and a well-known web presence to check with. I just have my own personal habits.
Like a lot of readers, I have a long TBR list full of great books I wish I had the time to get around to reading. A surprising number of those books I learned about online. Many in forums, but an equally large, or perhaps larger number from reading blogs. I can’t say for sure how many I learned about directly from the author’s own web presence. I’m sure a large number were recommended by other members of the online writing community.
I think that the majority of books I learn about through social media I learn of through the community as a whole, which includes writers pimping other writers’ books, but not a lot of writers pimping their own books. So it becomes hard to say whether web presence by a specific author has an influence on the sale of their books. Even in terms of my own buying experience.
What I can tell you is that I’ve bought a lot more books of recommendations or browsing the bookstore than I’ve bought books off my TBR list recommended by social media. There are plenty of books I’ve decided I want to read, but once I’m away from the internet, I forget titles or just am not exposed to enough immediate incentive to buy them, even if I loved them when reading about them on a blog or twitter feed.
In my experience social media definitely generates interest, but I can’t say that it’s actually gotten books out of the store and into my hands.
It’s something I greatly regret, and I always plan to make a stronger effort next time, but it does seem to be the reality that a strong web presence is not enough to generate actual sales.