Why would some think you're disabled?
That question popped into my head immediately too, Stealth.
There certainly are people with disabilities that have huge limitations. Going by what you said, timitmouse, I should tell someone in a wheelchair, because they are paralyzed from the waist down, to "Get out of that chair and walk/run! You know you can do it!"? Nah, I don't think so. Maybe I misunderstood the original statement?
Although I agree that people with disabilities are not able to do things exactly as a fully capable person can, I also do think that many disabilities can be overcome through willpower and/or technology. After all "necessity is the brainchild of invention"... In your example, you were just talking about the mechanics of walking, but this fails to address the spirit or purpose behind the activity. For example, if you take the act of walking as having the purpose of moving your body from one place to another, then a paraplegic can fulfill that underlying goal by use of a wheelchair even if they are incapable of performing the actual mechanics of walking. Likewise a paralyzed person can drive a car if the car is modified with hand pedals for the gas and brakes, a deaf person can talk on the telephone if the phone has a TTY attachment (which displays text of what the other person is saying), and a blind person can walk down city streets with the aid of a seeing-eye-dog.
After all, I think we are all impaired in some form or another. It may not be what most would consider a disability; it may just be a skill or trait that you don't have but another does. I cannot sew for the life of me, but that doesn't mean I am therefore subject to being naked. I'm also fairly short (for a guy -- 5'5") but I can still reach things on the top shelf of my kitchen cabinets with the use of a step-stool.
So I'd have to agree with timitmouse that people with disabilities can do much more than others give them credit for. And I'd also agree that FC is something that most anyone can do to earn some extra money, even if they suffer from some disability.