The sink object is so-called because it will asynchronously consume from any event stream that it is connected to, and then discard the events.  They are typically used to prevent dynamically connectable distributors from blocking, before they have any other connected consumers.  They can also be used as a means of reducing collection latency by instigation collections whilst the collector's consumer is processing a retrieved event.  They are also useful during development as a means of discarding 'as yet unhandled' event streams.