Another barrier will be the integration with their current "business intelligence" solutions. Microstrategy and Jaspersoft support is a good start, but what about Microsoft, Oracle and SAP offerings?

Switching to Amazon would involve rewriting your ETL process, and retooling your reporting software, and converting all your existing, currently-used reports.

A huge expense in data warehousing projects isn't the hardware - it's the consultants, the time, and the people to support the thing. I'm sure this is a great solution for companies looking to start a data warehouse, or maybe companies looking to revamp their reporting environment completely... but other than that it'd be a hard sell...