yes 1 minor impact is always on the cards in space and comes under the "shit happens" cause but if you have a lot of junk in low orbit its a major issue because that pile of junk stays there and keeps coming back around again every few hours until it kills you and adds you into the big pile of junk

if you watch the movie "Gravity" this scenario is what they show

If Elon/others get those space vehicles and colony plans off the ground in the future, here's hoping they'll figure out something to help with that(better materials, etc).

Someone forgot to tell Elon that Mars is a dead planet.

Well there's not many choices for colony sites in our solar system to begin with, and it's better in some ways than other possible picks.....plus it's a good potential source of resources.

No there isn't. No planet in our solar system has a oxygen-nitrogen atmosphere and most barely even have an atmosphere.

I know....that's why domes or underground colonies(sealed and filled with an atmosphere, of course) are our likely best bet.

Also even if we can't live on them long term, we can probably still harvest their resources.