Sorry to say it, but there's a giant, new problem for stressed out retailers this holiday season: your phone. The thing you use to dial home and make dinner plans is also a very real threat to the seasonal sales that can make or break their entire year.

Normally retailers have got us where they want us. All lined up and ready to bust down the doors at dawn. But suddenly our phones and their almost-always-on-network of friends' recommendations, digital deals and group buying power that tells us what, where and when to buy, are changing the rules.

Welcome to a new era in holiday shopping. I've seen people standing in malls in front of two competing stores checking ratings and reviews on their phone. I've seen them do it in stores at the shelf with product in hand. Comparing reviews and ratings before deciding to buy, or even shopping for a better deal with free delivery.

The retail mantra used to be: "get 'em there and we can close the deal." Now the sale doesn't even end with the consumer steps in store. According to comScore Q2 2011 State of US Online Retail Economy, 40% of smartphone owners use their phones to comparison shop while shopping at retail locations. What's more, 14% have actually abandoned the in-store purchase and bought the item from their smartphone, while standing in store. Simply put, if there's a cheaper, better, faster deal via the web than brick and mortar can offer, its goodbye customer.

There is some good news. According to Gallup, consumers are going to be spending more this holiday season. The bad news though: they're going to use their phones to determine if retailers will be singing holiday carols or the blues.

It used to be you'd go to a store to get expert advice. We're now either wise enough or cynical enough to know staff are pushing a product or upselling us somehow. Even official reviews online meet skepticism. Today we'll trust the opinions of strangers and friends that our phones deliver on any topic any time.

So, what's a retail marketer to do with this? Frankly, ask consumers for help. If you can't beat 'em, network 'em. Encourage people to check in, to post a comment, or write a review after a purchase. Use geo-based apps like Foursquare, Shopkick, or Facebook Places to offer a specials and discounts to anyone nearby. And remember social traffic drives online traffic drives store sales. The more check-ins, posts and comments your store receives on mobile devices, the more visible to potential shoppers you become.

Ultimately, retail is risky. Opening your store up to feedback will inevitably bring the bad with the good. But do it well, find new ways to engage shoppers socially and you'll point them directly to your door and your register. Now that 's a sale worth making.