Unless you've just emerged from a heads-down 72-hour hackathon, you know that the East Coast had some historically horrible weather yesterday. Hurricane Sandy paralyzed businesses throughout some of the most densely populated places in the country as the center of the 500-mile-wide storm barreled ashore in the mid-Atlantic states. Among other headline-grabbing disruptions, Sandy flooded the New York Stock Exchange, shorted out power stations in New York and New Jersey, sunk a replica of the HMS Bounty off North Carolina, shut down the Huffington Post, and wiped out a portion of Atlantic City's famous boardwalk. On a somber human note, the storm is already being cited for some 20 fatalities--10 of them in New York City--and officials fear that number may rise.

Eqecat, a firm that forecasts the cost of natural disasters, is predicting insurance claims could surge to $10 billion in Sandy's aftermath. "If Eqecat is correct, Sandy would rank as the fifth-worst hurricane in history, based on inflation-adjusted losses, according to the Insurance Information Institute," noted Reuters.

As infrastructure and public transportation collapsed, and customers prudently stayed home, entrepreneurs found their coping ability and ingenuity tested to the limit--along with their social media creativity. Many turned to Twitter and Facebook to stay in touch with customers and staff and the outside world. In the process, social media turned into a real-time record of small business survival tactics during Hurricane Sandy.

Staying in touch, even when the doors are closed

For Ricky's, a New York City-based cosmetics and costume shop with 10 permanent locations around Manhattan (and 30 more pop-up shops), the storm couldn't have hit at a worse time. Ricky's NYC founder and chairman Todd Kenig says Halloween sales account for about 20 percent of the firm's annual $50 million revenue, but Sandy forced to shutter all of its stores, as well as its corporate office, in the two days leading up to the holiday.

Like many businesses around New York, Ricky's took to Twitter and Facebook to share information with its customers, tweeting, "Due to circumstances with #Sandy, all Ricky's locations & Corp/Customer Service have been closed for today. Stay safe, everyone!" BaubleBar, the purveyor of women's jewelry with a retail store in New York's Flatiron district, echoed that sentiment on their Facebook page: "Because of Hurricane Sandy, The Bar will be closed Monday-Weds! We hope everyone is staying safe... (and stocked up on snacks)."

Online businesses suffered along with their brick-and-mortar counterparts, to the extent that they relied on New York-based data centers. According to several reports, sites went down as the storm surge dumped several feet of water into data centers around lower Manhattan. "You may have noticed that some of your favorite sites are down, including Foursquare," Foursquare tweeted. "We're hoping things will be back to normal soon!" 

Datagram, an ISP whose Manhattan servers host BuzzFeed, Huffington Post, Gawker--which all briefly went offline yesterday--was completely flooded, and waiting for the Army Corps of Engineers to assist in pumping out the water.

Plus, a few silver linings

Some entrepreneurial businesses, remarkably, managed to make the best of the situation. The breakdown of public transportation through the Northeast was a nightmare for most businesses, but for the on-demand taxi start-up Uber, it was an opportunity. "Subways may be closed but we're up!" the company tweeted at on point on Tuesday. "We have some cars available at the moment, and see more coming online."

One Uber customer, Mark Mazariegos,  tweeted in reply: "No trains... No Buses... No problem.. Thanks to @Uber_NYC"

General Assembly, the Manhattan-based hub of entrepreneurship, knew it would be closing its offices and coworking facility, but that didn't stop the company from offering a lives stream of its classes--for free. "Be safe. Be careful. And if you can, be learning," the company posted to its Facebook page. The post generated 40 "likes" and plenty of goodwill towards the company.

Another company received a decidedly less favorable response to its attempt to cash in on the storm. American Apparel blasted customers with an e-mail titled "Hurricane Sandy Sale," offering customers 20 percent off "in case you're bored during the storm." The e-mail blast drew outrage from storm-sensitive Twitterati. One user, Buzz Bishop, tweeted "@americanapparel will soon be hiring a new marketing director. Yes, they just email blasted a 'Hurricane Sandy Sale'."

"I think this demonstrates how Instagram is quickly becoming a useful tool to see the world as it happens – especially for important world events like this," Kevin Systrom, founder of Instagram, told The New York Times.  Jack Dorsey, founder of Twitter, was even more succinct. "Proud of Twitter right now," he tweeted yesterday evening.