A good architect should lead by example, he (or she) should be able to fulfill any of the positions within his team from wiring the network, and configuring the build process to writing the unit tests and running benchmarks. Without a good understanding of the full range of technology an architect is little more than a project manager. It is perfectly acceptable for team members to have more in-depth knowledge in their specific areas but it's difficult to imagine how team members can have confidence in their architect if the architect doesn't understand the technology.
All too often software architects sit in their ivory towers, dictating specifications, technology decisions, and technology direction to the developers below. More often than not this leads to dissension in the ranks, quickly followed by a revolt by the masses, finally resulting in a software product that doesn't even come close to resembling the original requirements. Every software architect should know how to communicate the goals and objectives of a software project. The key to effective communication is clarity and leadership.
Why? Was it because they chose Ruby over Java, or Python over Smalltalk? Or because they decided to use Postgres rather than Oracle? Or did they choose Windows when they should have chosen Linux? We've all seen the technology take the fall for failed projects. But what are the chances that the problem was really so difficult to solve that Java wasn't up the the task?