The acquisition and failure to discard possessions that appear to be useless or of limited value. This describes the behavior that many of us engage in.
It is not really a problem, maybe an eccentricity, unless we see the other two features of the definition:
Living spaces so cluttered that using the room as intended is impossible.
The third defining feature is significant distress or impairment in the ability to function.
People experience distress at the possibility of throwing things away, and at the Herculean effort it would take to clean up the house.
They develop avoidance to decision-making and discarding.
They avoid putting things out of sight.
We think hoarding behavior is in large part an avoidance behavior.
-Randy O. Frost. Ph.D., Speaking to the New York City Hoarding Task Force, 94.