Last year at the Software Architecture conference I saw a presentation by James Thompson on "Beyond Accidental Architecture". Afterward he and I got to talking about the topic and my position that everything is really about scope of work and scope of influence and the difference between a senior architect and a junior developer was not in the kinds of problems being solved, (time, complexity, interfaces, etc) but in the scope. Systems, platforms, and frameworks vs classes, functions and interfaces. 3 year roadmaps vs sprint planning. Raising the effectiveness of a team vs a brown bag on a new library. Bridging the gap between disciplines (legal, finance, product) vs between developers on a team.
And not just what, but how. The wider the scope, the less direct control there is and the more influence is needed. You don't get to tell folks what to do, you work with them to find shared solutions and raise the bar for everyone. Which brings me to James' follow-on article about the "Software Architect as Guide" It's an interesting take and one that really resonates with me.