I was slightly alarmed to read recently in a document describing a particular adaptation of the unified process that allowing architectures to ‘emerge’ was a poor excuse to avoid hard thinking and planning and that emergent architectures, and anyone who advocates them, should be avoided.The term ’emergent architecture’ was, I believe, first coined by Gartner (see here) and applied to Enterprise Architecture. Gartner identified a number of characteristics that could be applied to emergent architectures one of which was that they are non-deterministic. Traditionally (enterprise) architects applied centralised decision-making to design outcomes. Using emergent architecture, they instead must decentralise decision-making to enable innovation.
Whilst emergent architectures certainly have their challenges it is my belief that, if well managed, they can only be a good thing and should certainly not be discouraged. Indeed I would say that emergence could be applied at a Solution Architecture level as well and is ideally suited to more agile approaches where everything is simply not known up front. The key thing with managing an emergent architecture is to capture architectural decisions as you go and ensure the architecture adapts as a result of real business needs.