The argument for free
As a comment on one of my older posts, a reader asked which would you rather have: a handful of book sales of your self-published book on Amazon, or thousands of readers gained by giving the book away?
The limitations of free
People download tons of free ebooks and never actually read any of them. I was on the mailing list of several free ebook services but I've unsubscribed because my Kindle is full of books (mostly not free ones) that I haven't had time to read yet. So going free may lead to thousands of downloads, but nobody knows how many of those will ever be read.
Free as a way to prime the pump
If you can manage to target readers effectively and if you have several books in the same genre, it can make sense to give the first one away free in hopes that readers will then go on to buy others.
However, targeting readers these days costs money. One expert I talked to feels that currently Facebook ads are the best medium for this. You can risk a relatively small amount of money to see whether the ads lead to sales and justify the investment.
In his opinion, free social media doesn't work for unknown authors of fiction (although I'm sure, as always, there's are exceptions).
Do shoemakers do this?
The other point this raises is why this choice seems to come up only for writers and artists. I don't think shoemakers debate whether it's better to charge for their shoes or give them away so they can have the satisfaction of seeing more people wearing them. They expect to be paid for providing something of value, and I think it's reasonable for authors to expect the same.
Of course, that requires authors to convince potential buyers that what they are offering does have value. That's going to require us to be as creative in marketing as we are in spinning stories.