What is the threshold of detection for small orbital debris? How small can something get before it can no longer be reliably tracked (and therefore avoided)?
Given that collision energy is dependent on the delta-V of the parties to a collision, and that some extreme cases may be unlikely or absurd e.g. geosynchronous vs "retrograde geosynchronous(?)", how much collision energy could an untrackable debris item deliver to an unsuspecting space vehicle? In other words, how bad could the "hidden hazard" actually get?