Damien Katz says:
"The real future of cloud computing about being a simple, low cost, high availability way to get your data and applications online, saving you the cost and hassle of building and maintaining your own infrastructure. You aren't just saving yourself from building a cluster, but from installing applications, applying patches, monitoring security, keeping backups, etc. Your cloud provider maintains the applications while making sure your data is safe, secure and accessible. They worry about the infrastructure so you don't have to."
Will said - and quite apropos for Heroku.