There are 29000 pieces of debris in LEO larger than a cubesat, and 670000 larger than one cubic centimeter but smaller than a cubesat[1]. While space junk is a problem, a couple of cubesats are not making any difference. Space is big, even LEO, enormously big. Small particles like engine exhaust are a problem (they can cause pitting, etc), not large objects. Or you know, China blowing up its own satellites is also a big problem[2].
> Small particles like engine exhaust are a problem (they can cause pitting, etc), not large objects
Tell that to Iridium, who gets too many collision warnings a week to act on them, and lost of functioning satellite. The collision was between 2 large objects for the record.
[1] http://www.esa.int/Our_Activities/Space_Engineering_Technolo...
[2] https://en.wikipedia.org/wiki/2007_Chinese_anti-satellite_mi...