The function of the library has been evolving ever since the advent of the internet. Libraries have long granted their patrons access to paper subscriptions, but they can now offer services that were not obtainable before computer networks were in wide use. One such service libraries can offer is access to digital databases for genealogical and family history research, a service that, I think, has a much broader appeal to the general public than do obscure academic journals and manuscripts.
In particular, Ancestry.com's Library Edition is being purchased by libraries across the globe. It seems to me that Ancestry Library Edition—which appears to cost about one or two thousands dollars per year—is a good value for a library seeking to offer a genealogy resource to their patrons. There do not appear to be any significant competitors to Ancestry.com, which claims to have over 6 billion family history records in their database at the time of writing. In my view, the trend of interest in genealogy and family history is here to stay; it is becoming economically feasible and technologically convenient for typical people to seriously investigate their own origins. After all, what is there for the average person to do in life after the standard rituals of celebrity gossip and drinking to excess? Even the most mindless people reach out for some shred of meaning in their lives, and will discovering the traces of their ancestors not become a seductive and irresistible pastime?
Of course, if it becomes standard practice for libraries to pick up Ancestry Library Edition, it will tremendously boost Ancestry.com's revenue and brand exposure. Patrons who begin their family trees at the library may well decide to purchase a home subscription to continue the endless quest. If the current trend continues, the shares of Ancestry.com stock should be worth much more a few years from now.
Disclosure: the author owns shares of Ancestry.com (ACOM)