schizanon, 
I get that #AWS #SQS is a "pull-based" message bus, while #SNS is "push-based", but given that I don't understand why SQS exists.
Push seems superior, so why involve a #queue at all?
But fanning out SNS events to SQS #queues is a recommended pattern, why?
What can you do with a poll-based queue that you couldn't do with a push-based #pubSub?