I've known for a while that debit cards and hotels don't really mix, but now I've learned it the hard way.

Last weekend, I stayed at an Embassy Suites in Florida, attending a magazine writers' conference. I had a wonderful, spacious room with all of the amenities, and the service was great, but like many hotels, Embassy Suites immediately put a "hold" on the money for the two nights I was staying. I had deposited a check that day at my bank, but because they were holding most of my funds until the next morning, I went through the late afternoon and evening, oblivious to the fact that I had almost nothing in my bank account -- and yet, plenty of unavailable money.

I discovered what had happened that evening at a restaurant when my debit card was declined. But that's another story entirely, although happily not one that ended with me washing dishes.

Fast food restaurants and grocery stores test-market products all the time by slipping them onto the shelves. So often, in fact, that average consumers may not even notice when they've tried something impermanent. But hotel rooms are a different beast. Renovations are expensive, so they can't just remodel rooms and cross their fingers. And sometimes, ideas that looked good on the drawing board turn out to be hitchy in practice.

Most of the big brands conduct most of their experiments behind closed doors. According to an illuminating exposé from Portfolio.com, Starwood (Westin and W Hotels), Hyatt's Summerfield Suites, and Marriott all run mini-properties stashed in private locations such as warehouses and office basements. Loyal customers are quietly invited to give new rooms a whirl, although they're not usually allowed to stay overnight.

But Hilton operates a wing of an otherwise anonymous Los Angeles-area hotel specifically for the purpose of trying out new room ideas. Regular guests check in and out of the test rooms, conveniently located near Hilton's corporate offices. To ensure that only brand devotees are exposed to potentially disastrous experiments, its El Segundo Hilton Garden Inn property (which is the only one of the 260 HGI properties that Hilton directly owns and operates) assigns the prototype rooms only to people with Diamond frequent-stay status. That translates to folks who stay in Hiltons for about two months a year.