I think this question, like any question of personal identity, is answerable only in personal terms. I consider myself to be a runner, although I currently run only 4 days a week. But running is an activity that is meaningful to me, and a portion of my identity comes from my participation in it. To try to base a definition of what a runner is on how many times or how many miles per week one runs, what accessories one uses, or one's race times, is inherently pointless, because in the end, all of our performances are meaningful only to ourselves. I'm working my butt off to try to break three hours for my fall marathon, and if I do, who will care? Only me. If I run 2:59:59, I'll take great satisfaction from that effort. There are those who would look at that same result as a catastrophic failure, but for me, it would be a success. Those who attempt to define a category that excludes those slower or "less dedicated" than themselves are doomed to failure, because eventually all of our efforts will be forgotten, our records (if any) will be surpassed, and no one will remember what we accomplished, if anyone paid any attention at all. Except for us. If I never break 3 hours, I'll still take satisfaction in qualifying for Boston, and that will remain with me for a long time. You're a runner if you run, and if you say so.