Lots of them one in May, the Woman lost her job as a Nurse for charging time she did not work the Man was laid off from his mechanics job.  Found power bills over $6K, student loans that they had not made payment one on even when working her wages were being garnished.  They were evicted and homeless.  Over a hundred pairs of shoes in the locker mostly expensive sports shoes but all moldy or worn out.  Looked like even when they had money they did not pay bills for anything.  The story they did not pay any bills so why would they pay their locker rent.
I find eviction notices in most every locker sometimes many of them.  Always months behind on rent.  Most of them are on Welfare and most of the lockers have either Bongs or crack pipes in them.  Drugs are one of the biggest reasons near as I can tell.   

I have bought 2 lockers from people I know and some other close connections.

One a big locker (10X 20) full of household stuff from a guy who had coached my sons baseball teams. He had a drug problem and lost everything. Found old pictures of the teams he had coached with my sons in them. Pictures of his daughter who my oldest son went to school with. The household stuff was dirty and worn little value I paid $400 cause it was a huge locker and I lost about that much on it. It was heartbreaking to me as it was obvious he was living in the locker for a while and I hear he is homeless and his son is having drug problems just like his dad.  The guy was a dead ringer for Randy Johnson about 6'10" and lean.

The other was a small locker full of misc that had been owned by a guy who ran a gun shop briefly. He got in trouble for not paying his bills and not paying off consignments.  I had frequented the shop when he was running it and know the gunsmith who he sublet from, he was over $10K in arrears on rent when he skipped and had borrowed money from the gunsmith to begin with.    He has people looking for him so he skipped to Alaska. It is not wise to steal from people who are well armed. It was a great locker lots  of ammo, holsters uniforms and badges and I only paid $30 for it.

In another locker I found a picture of one of my wife's cousins. No idea the connection but there he was.

Another locker I found an engineering notebook from 1959. In it was the name and phone number of someone I go to church with who had worked with the guy in 1959. 

The auctions I go to take Credit or Debit cards.  So since I have cards with limits of $30K each it is not a problem with me. Now paying off the card me be an issue but buying the locker is not. I have seen a few people not pay and they are not allowed back period. Most people know how much they have to spend and do not go over it.  I try to not spend more then i have in cash but a couple times I have used debit cards never credit.

I have seen as many as 5 or 6 locks cut in the same locker. Not normally a good sign my experience is most of the lockers with many cut locks have been gone through and the best stuff taken out. Not always but often.

Got on in January 2012 that had been rented in 1982 so 30 years. Had not been touched since rented the guy moved to CA and left stuff here.  He died 8 years ago and his girlfriend kept paying till she died late 2011. Was very good locker, high end fisihing gear, a belt with silver and gold buckle lots of neat things.  Paid $275 made at least 3 times that and still have the neatest stuff left. Got one in the summer that had been in st0rage 24 years adn it was a total bust. Find a lot that have been rented more then 10 or 15 years.  Not always any good but the potential is there.

Best A big locker full of junk/trash for $50. Found $4350 cash plus a few hundred in goods. A hoarder he kept one dollar bills and change were over $2500 in ones alone.

Second best a lock from a guy who used to own a gun store. Paid $30 Got about $500 worth of ammo alone still selling holsters and I have kept some cool items like a firefighters coat and badge. Looked like it had been gone through but it had not. Just messy.  I know the guy and also know that a lot of people are still mad at him after he stole the money from their consignment guns.  He is not in the state anymore. Easy made a $1000 on that locker already.

Close tie a locker full of what looked like old stuff for $700,  a Sterling tea set 70 ounces of Sterling.  About $500 in other stuff.

Worst a 10X30 full of junk spent $40 on the locker $200 at the dump and got nothing out of it. Was a dump the #1 move in special loaded with trash and abandoned oh it had flooded as well.

Have to mention the worst so all the Newbies do not expect to find treasure in every unit. I have done well over a 100 lockers now and 3 really great ones a dozen okay and a lot of bad ones.

If not being on site causes you to overbid, then you're better off skipping the day of work, it'll be cheaper in the long run.

Well since a day at works is worth more then $300 to me if I overpay a bit but would have held back in person it would not be a big deal. 

Somebody trying to cash in.  I have heard of several such attempts here in the Puget Sound region.  Several  lockers that appeared to be full of nice antique furniture and sold for several thousand dollars each. Well all the furniture has major issues which are hidden from view and was worthless.  The renter was determined to be the same guy and a known shyster, he was confronted by one of the buyers and the buyer demanded his money back and got it.  The threat was a severe beating. Enough said as much as the guy deserved a beating it is not worth going to jail over. it appears to have stopped for now but with state law requiring the renter get any amount over what is owed this may continue to happen just not as obvious. It would be easy to stage a unit to look great when all it had in it was junk. Boxes labelled as stated in the OP are a big clue something is wrong.