I've been a professional storage buyer for nearly 7 years, purchased roughly 1000 units (both online and at live auctions). VERY few facilities tamper with the contents of a unit before it goes up for public sale. Not to say that it doesn't happen, but it is rare... especially at the big corporate chains (Life, CubeSmart, Public). The reason is pretty simple actually... the original tenant has the legal right to settle their debt right until the moment the unit is sold... and actually even after (many facilities allow the tenant to pay and reclaim their unit even after it is sold, if the winning bidder has not yet paid in the office). If the facility owner were to plunder the contents before the auction, and the tenant were to pay up at the last minute (which I have seen happen MANY times), the facility could face severe legal issues. Some tenants actually keep insurance policies and file an itemized list and photos of the contents with the insurance company. The storage business is a numbers game... owner's make their money from rent, not from a few bucks here and there from junk they can sell out of units. It is not worth risking their entire business (10's of thousands of dollars for small facilities to possibly millions for the big chains) just to make a few hundred. Plus, these owners likely don't want to to the leg work to sell the items... they are property owner/managers, not resellers. It's hard to understand this, as we have a treasure hunter mentality, but most people don't want to dig through other people's "junk", even if given the chance.
Now, there are a few scenarios that may look like the owners illegally searched the unit, but didn't. 1.) The original tenant knew they were going to default, and took what they wanted 1st, not wanting to deal with the disposal of the unwanted items. This happens a LOT with estate units, where the family doesn't want to deal with the bulk of items, but knows to take "grandma's jewelry" 2.) Some tenants will sign their unit over to the facility in lieu of their back rent... in this case, the facility need not follow lien law, as the unit is now the property of the facility. 3.) If a lien unit is a "no sale", it also becomes the property of the facility. In both cases, the facility can legally do whatever they want with the contents. They may put these units up at auction with actual lien units. Now, I personally feel they should indicate to buyers if a unit is a true lien unit or one of these "manager's specials", but they are not legally required to do so.
Certainly, there are some facilities that play fast and loose with the law, and roll the dice, but I'd say that it's less than 5% in my experience.