Running is arguably one of the worst things you can do to your body, despite it's efficacy in improving your cardio performance. It's bad on your joints, your bones etc. Swimming and cycling are much much better.
That is decidedly untrue. The big problem with cycling and swimming is that they are low impact and don't stress your bones an joints enough. Your joints and bones are just like any other tissue in your body. They respond to stress by getting stronger and when they are not stressed they get weaker. As in all things you can of course over do it, but the amount of running the average person would do (15-20 mpw or less) is very beneficial to bone an joint health.
based on the new runners I've observed on sidewalks in the last 12 months I have to say proper form seems very difficult (/expensive, given need to hire a coach) to achieve.
Most people will instinctively run with decent form as long as they're not obese or already injured. Coaching can be helpful but usually isn't essential.
I'm as wrong as possible with this. I still believe that swimming and cycling are better for you, but the injuries I was concerned about (and personally experienced) are more typically associated with overworking your joints/bones/tendons and ligaments.
