When I published my first book in 2010, I was open to giving away some free copies. This was mainly through a contest in an online women's magazine (which may or may not have sent my books to the winners) as a way of finding new readers. In the end, this experiment was a failure; and although I've given away free books (both paperback and ebooks) since that time, in most cases, I'm sad to say that the books are often not even read, let alone reviewed. So, any hope of bringing in future sales or even feedback gave disappointing results to this experiment. This has led me to believe the old idealogy that people don't appreciate anything they get for free.
Of course, it's not always true. I find that usually, it's my most loyal readers that appreciate a free book now and then, and in fact, it's for those same people that I write for in the first place. Loyal readers are the first to give me feedback, reviews, and tell others about my books, and in fact, the people that writers should value the most.
It's not my place to tell other authors what to do. My experience might be different from someone else. It's hard to say. I just feel like when you give something away for free, it can sometimes lose its value. I also know that writers spend a lot of time and energy writing books, that these characters are very close to their hearts, and like anything close to the heart, you must be somewhat protective. You must see that it has value and make sure others see this too.