I am pretty sure `replayLazily` ensures we run our authentication code once, then supply the same result to all interested parties (via `-[RACSubscriber sendNext:]`) using a multicast connection, right? (Is this just using RxCocoa convenience methods to do what Justin outlined [in this SO response](http://stackoverflow.com/a/14072445)?)

Does `defer` here serve simply to make sure the login code isn't evaluated when we call `replayLazily` (which I assumes subscribes to the signal), but instead to wait until someone subscribes to the multicast connection provided by `replayLazily`?