There is a space junk problem, and unfortunately, the amount of space junk orbiting the Earth is only increasing, and will continue to increase over the next few years.
Space junk is essentially the name given to all dead satellites that are left over after it runs out of power and eventually dies while in orbit. Space junk can also be spent rocket materials, or debris from satellite collisions.
Unfortunately, no plans have yet been successful enough to launch into space to begin pulling our junk back to Earth, so all of it continues to orbit the planet at a high rate of speed. As the junk pile grows, we make space travel more dangerous; it would be catastrophic if a piece of space junk flew into one of our rockets.
Cubesats and smallsats are becoming more popular because of their inexpensive production and lightweight, but because there are so many launched at a time, they threaten to increase the amount of space junk surrounding the Earth exponentially.
We will have to find a solution to the space junk problem soon, or someday space exploration will become a thing of the past.