While this is very true that there is a steep initial payment curve, many companies can afford to fit this minimal bill considering the cost of running their own dedicated machines. I think it's quite beneficial that there is OOB support for MongoDB, CouchDB, Amazon RDS, ZeroMQ, Gearman, Memcache & Memcached. Assuming some of these queues scale out automatically, there's a huge benefit in reducing the complexity of your application layer if you're trying to do some rapid prototyping for a minimal viable product that still has the balls to scale out if necessary.