It's a very real concern. There are extensive regulations and procedures for having and disposing of assets in orbit. When you put something into space, you can't just choose any old path. Orbital trajectories, especially geosynchronous ones, are highly valued and some missions require very specific flight paths. If a unit becomes unresponsive in a critical orbit for a communications network, the entire system cannot as easily adjust it flight path because now there's a new hazard there.
Right now, the probability of hitting something is fairly low. But collisions do happen. Last year Iridium lost one of their satellites when it collided with a large deactivated Russian satellite, creating a very large and hazardous debris cloud. Crashes like that accelerate a scenario called Kessler Syndrome. This is when the amount of mass in space is high enough that large collisions begin happening. Those collisions create even more debris, increasing the amount of collisions at an exponential rate. We can track everything in space above 5 cm right now, but scrap even smaller than that can cut through just about anything we can put in space right now.