I wrote a singleton just the other day. I dont often write these but occasionally they are useful.
It enabled us to decouple some code deep down in our architecture and enforce some constraints around the use of this particular piece.
When you actually need a singleton it's best to use one and call it out as such so people know what they are dealing with. Dependency injection will often be passing around a singleton everywhere without people being aware that it's a singleton and all that that means.
