dependency injection scopes

I'm reading wirebox wiki and trying to figure out the correct scope
for what I am doing.

If I do the below then I get an object in the NOSCOPE scope, meaning
it's transient and gets created when requested. Meaning that I can
have multiple of these?
map("userService").to("model.userService")

Is this the most efficient? Should I create this as a singleton
object? Maybe if I do create it as a singleton and have mutlitple end
users accessing the system then the object will have whomever the last
person that access the objects data in it causing simulatanous aces
issues? I'm wondering if I am over thinking?

Anyone have or can tell me where to find a document that explains when
to use what scopes?

Thanks.

Jonathan

If you do not provide a scope, it defaults to the variables scope.