Across the country, people are losing the items they've placed in storage units.

Surveillance video at one Missouri storage unit shows a pair of thieves operating in broad daylight. The thieves take out a bolt cutter, clip off the padlock on an outdoor unit and begin loading their minivan with items from the unit - including family mementos, generators and even a large leather couch, which they strap to the roof of the van.

It's a wake-up call for the estimated 11 million Americans who pay self-storage facilities monthly fees to store their belongings. Personal treasures from storage units are an increasingly easy target.

Carol Lajoie bought a padlock and insurance for her belongings when she put them into storage in San Jose, Calif. Thieves broke into the unit and made off with $10,000 worth of Lajoie's possessions.

"Most of it was family items and it was hard to put a value on it," she said.

Insurance only covered $1,000 of her claim.

Brad Garrett, a former FBI agent and ABC News consultant, said it was difficult to "assess storage theft only because most of it, I think, does not get reported."

He said the biggest problem with temporary storage facilities is that they aren't built to store luxury items, such as expensive china or Persian rugs.

"The locking systems are extremely poor and the ability for people to go into them twenty-four hours a day sort of make them ripe for people to steal items if they have a pass to get in," he said.

That's why consumers need to do their homework before they decided on a storage facility, Garrett added.

"In other words, what type of camera systems do they have? What are the locking systems? Can you control the type of locking system? Who has access? Do they have cameras 24 hours a day? All of those questions need to be answered to your satisfaction before you store anything there," he said.

"Deciding whether you want to place your goods at a temporary storage facility is really driven by you doing your own homework."