Ian Cooper on Hexagonal Architectures at Agile Yorkshire

The term 'hexagonal architecture' has come back and forth in popularity since Alistair Cockburn first mooted it, with the Rails community's recent soul searching over its importance or threat just the latest. So what is a hexagonal architecture, why might you want to use one, and why is the 'Rails just falls away' threat so discomforting to web framework builders. In .NET how can we make 'ASP.NET just fall away'.