There has been a lot of discussion lately about the problems with using (and overusing) Singletons. I've been one of those people earlier in my career too. I can see what the problem is now, and yet, there are still many cases where I can't see a nice alternative - and not many of the anti-Singleton discussions really provide one.
Here is a real example from a major recent project I was involved in:
The application was a thick client with many separate screens and components which uses huge amounts of data from a server state which isn't updated too often. This data was basically cached in a Singleton "manager" object - the dreaded "global state". The idea was to have this one place in the app which keeps the data stored and synced, and then any new screens that are opened can just query most of what they need from there, without making repetitive requests for various supporting data from the server. Constantly requesting to the server would take too much bandwidth - and I'm talking thousands of dollars extra Internet bills per week, so that was unacceptable.
Is there any other approach that could be appropriate here than basically having this kind of global data manager cache object? This object doesn't officially have to be a "Singleton" of course, but it does conceptually make sense to be one. What is a nice clean alternative here?