Replying on a different post, I just remembered that I had cards from three different library systems when I was a kid: St. Clair county, Henry county, and Lakeland (my elementary school). I got the Henry county card by using my grandparents' address -- the only fraud I ever committed.
I did this primarily because I wanted to read every single Nancy Drew book in order and no library had the complete set. I accomplished my goal, but each library had such different collections that even after I went into home education I continued using both county systems until I moved away.
I probably always would have become a prodigious reader, but I think juggling all of those different libraries as a child set me on the book-lined path of literary excess I still trod today.