is it true that Amazon's EC2 clouds had some failure that lead to a permanent data loss?
Yes, earlier this year there was a failure that resulted in permanent loss of data on a very small percentage of EBS snapshots.
As for 'clouds being the next big thing' there's a direct correlation between amount of media hype, and the amount of under-qualified hosting companies moving in to this market to grab share. Cloud hosting is now only second to SEO in terms of being a web service attracting BS product and marketing, so the chances are high that you'll see further failures of cloud resilience in the future.
Every computer, or system of computers, will at some point be subject to some degree of failure. Why would EC2 be any different? The difference between the failure on EC2 and other systems however is that with EC2 it tends to be less frequent and more easily/quickly recoverable.