How did Amazon's cloud computing business do in the fourth quarter? That's not an easy question to answer. Amazon lumps its web services business together with other non-retail activities under "Other" sales.

But given the growing buzz around cloud computing, and the fact that Amazon was a frontrunner in this area, there's growing curiosity about how the company's web services unit is performing.

In Q4 2008, Amazon's "other" Consolidated sales -- a category that includes Amazon Web Services, Amazon Enterprise Solutions, miscellaneous marketing and promotional activities, and co-branded credit cards -- was $175 million, up 33.5 percent from the same quarter a year ago. For the full year 2008, that category was $542 million, up 41.5 percent over the previous year.

In yesterday's Amazon earnings conference call, the first question was on one of the company's cloud computing initiatives and whether it's making progress in attracting large enterprise customers.

Jeff Bezos' response was vague.

"We think there is very significant and meaningful opportunity over time for enterprise level customers with our web services business," Bezos said. "Elastic Compute Cloud and Simple Storage Service are already being used by enterprise level customers and we expect that trend to continue."

Amazon is famously secretive and doesn't reveal details of any business or product until it's ready. But some are calling for more details about Amazon Web Services (AWS). InformationWeek writes, "Unfortunately, Amazon doesn't break out AWS revenue separately, though it should, and it will come under increasing pressure to do so."