1) Reconstruction of Shredded Material - discovering papers not thoroughly shredded in trash cans, bins, dumpsters, etc.
2) OSHA and Potential Fire Hazards - "in-house" shredders are potential fire hazards due to dust build-up, "clogging", etc.
3) Certified vs. Uncertified Destruction - proper shredding techniques (chain-of-command, logging activities, etc.)
4) Witnessed Destruction - the destruction of sensitive materials must and should always be witnessed by another party or parties
5) Background Checks - employers typically use hourly personnel to shred "in-house" which most do not require a background check upon employment.
6) Disposal - usually thrown away once shredded with the regular trash.
7) Cost - equipment costs, wages, etc. vs. a shredding company hired to do the shred is much higher in the long run.
8) Disgruntled Employees, Former Employees, Infiltrators - they will do whatever they can to harm a former employer or business.
9) Security - locked containers only accessible with a key; much more secure than trash cans, dumpsters, etc. which are accessible by all.
10) Greatest Defense Against Obstruction of Justice Charges is a Scheduled Shredding Service - Businesses being protective of their sensitive materials helps their liability issues.