One of the things that makes an architect is experience, and in many cases an architect has got where they are because of the expertise that they've built up in their chosen technology; be it Java, .NET or whatever. I'm still of the opinion that it's perfectly viable to be an architect with a particular technology focus (e.g. a Java architect) but there is always a danger that everything will start to look like a single technology solution.
In a way, this is inevitable. If your experience is mainly in technology X, then you're going to feel comfortable designing systems in technology X. Of course, this doesn't necessarily mean that technology X is the best solution. An example that I always cite is that most of my background is in building Java systems; from client-server and web apps through to distributed systems and service-oriented architectures. A few years back, Swing would have been my first choice of technology for building a desktop application. Ask me know though, and I'd lean towards a .NET or RIA client, but ultimately it depends on a number of things. In this case, the influencing factors include the skillset of the team, existing vendor relationships, politics, supported desktop platforms, desktop deployment policies, operational/support requirements and so on.
Being open to other technologies is a hard lesson to learn and, as we've seen on the architecture training course, it's natural for people to stick to their tried and tested technology set. As an architect, you should certainly let your experience guide you in making the right decision. Having said that, you shouldn't let it constrain you.
Simon is an independent consultant specializing in software architecture, and the author of Software Architecture for Developers (a developer-friendly guide to software architecture, technical leadership and the balance with agility). He’s also the creator of the C4 software architecture model and the founder of Structurizr, which is a collection of open source and commercial tooling to help software teams visualise, document and explore their software architecture.