When a company or organization loses a customer, they typically want them to come back. I think libraries do too, as a general rule. Of course, we don’t just want them to come in, or “just” get a library card, or even just check out a book. These are all measures libraries in the U.S. as benchmarks (there are many others of course!), but they aren’t necessarily great indicators of library use, in and of themselves. Are people using your online resources? Are they attending programs? Are them coming in to read the newspaper, use the photocopier?
It doesn’t sound like the new customer relationship managing tool built by Charlotte Mecklenburg Library tracks all of those things, but it does track some of them. And when a user is found to be inactive, they get an getting an email saying the library misses you. These emails have brought back 13,000 people so far. 
It’s an interesting project, and an interesting article. How do you bring back users who have gone away from your library?
A Life in Libraries 