title_body: Did any other publisher follow Baen's approach of freely releasing older e-books (especially for series)? According to Eric Flint's Prime Palaver, publishing older books as free e-books as Baen did with Baen Free Library may be a good thing for business (I asked a related question to verify that claim).
  
  As such, I would expect other publishers to also adopt a similar business model.
  
  Has any big publisher done so? (So to avoid definition squabbles, I'll arbitrarily limit this question to houses that publish books for at least 20 authors and releas at least 100 books a year).
  
  If not, did any of them state why they didn't?
  
  For those who didn't read the link: this has nothing to do with digitizing random books. The idea is to take a series of an author you are already publishing; and release older books (published by you, so you already have a digital copy from having published it) and posting a free e-book of that book online, so as to hook in new readers into the series/author/publisher).
upvoted_answer: It has become very common for publishers to provide free copies of the first book in a series. So common that the ebook deal site BookBub has pages of links to free ebooks - some deals are ongoing and some just for a limited time.