My comment about lack of source information is based on recent direct experience. This "database" contains images of published books, but Ancestry's source citation, source information, and source description do not identify the book. I observed this recently when Ancestry gave a me a search result that pointed to this database. The book was recognizable as a page from the early-20th-century "Lyon Memorial" series (books that are in the public domain and are available on several free websites), but Ancestry's source information didn't mention that, much less mention which of the several "Lyon Memorial" volumes it was. I used other search capabilities to figure out which of the books it was, and I gave no credit to Ancestry when I cited the book as a source.
PS - Randy Seaver's Genea-Musings blog post describes the index entries in Ancestry. Although many Ancestry users seem to build their entire family trees from index entries, the image of the record (in this case, the book) is just one click away from the index entry. It's the citation information connected to the book image that I found to be so appallingly deficient. (I never pay much attention to the index entry -- as I see it, that exists only to help me find the record.)