I don't know much about colliding dots but ..
The volume of space from surface of earth up to about 200 km is roughly 1 to the 20th (cubic meters). The volume of a spherical spacecraft with a diameter of 5 meters (slightly larger than a cubesat) is about 500 (cubic meters). Assuming 10,000 of these spacecraft orbiting earth (a bit of an overestimate) we have a total volume of 5 times 10 to the 6th (cubic meters).
At any instant the chance of randomly introducing a new object into an occupied position is on the order of 1/2 times 10 to the -13th power.
Of course I have omitted a few important details (and I haven't checked my arithmetic) but since this is about 10 to the 7th less than the odds of being hit by lightening if one lives to be 100 I wouldn't worry about it too much (however, I would take reasonable precautions with lightening).
K2ubc