As the US Gulf Coast reels from Katrina's devastation, online businesses are struggling to gauge the impact of the possible loss of half a million prospective customers for weeks or months.

The New York Times reports (5 September) that, according to comScore Networks, an internet research and consulting firm, 860,000 people, on average, surfed the web from their homes or offices in New Orleans and the Mississippi towns of Biloxi and Gulfport each day in the week preceding the storm.

The newspaper says that online travel agencies like Expedia, Travelocity and Orbitz are no doubt feeling the pinch more than most online retailers. Not only must they cope with a deluge of calls from customers who had booked trips to the Gulf Coast and now want their money back, they must also face up to the possibility of a slump in sales as some vacationers and business executives deterred from flying to New Orleans drop their travel plans altogether.

According to the report in the NYT, with Mardi Gras just six months away and recovery estimates for the city still cloudy, agencies cannot even be sure that one of the prime travel events of February will occur. Even if the city is in a position to stage Mardi Gras events, travel companies cannot say how many travelers New Orleans will be able to accommodate.

The NYT says that Travelocity this week sent e-mail messages to 14,000 customers who had booked flights, hotel rooms and car rentals in the afflicted areas. The company has also waived the cancellation and rescheduling fees it typically charges customers, as have most airlines and other travel companies.

The newspaper reports that general merchandise retailers on the web say they have not experienced significant dropoffs in sales, at least yet. EBay, for instance, notes that it has 157 million customers worldwide.

The web's biggest online retailer, Amazon.com, is holding an undisclosed number of packages for customers in the affected areas. An Amazon spokeswoman, declined to discuss the financial impact of the hurricane on the company.