Is Microsoft's claim of 250 million SkyDrive users fuzzy math?

Tally likely includes one-time users and users of Windows 8 and Windows Phone, which automatically sign them into SkyDrive

Microsoft's announcement this morning that it has 250 million SkyDrive users sounds impressive.

I'm suspicious that there could be some fuzzy math here, a bit like Microsoft's counting of enterprise Office 365 users. We asked Microsoft for further clarification, and the company declined to say anything else.

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In its blog post, Microsoft specifically says it has 250 million "users" of SkyDrive. I'm wondering how active they are. These days, there are many ways that people get signed up for SkyDrive accounts, but that doesn't mean that they're actively using the service.

For instance, signing into Office 365 for the first time gives you a SkyDrive account.

SkyDrive is also one of the Microsoft apps that comes preloaded on Windows 8 machines. Signing into Windows 8, which users do each time the computer starts, also signs users into a SkyDrive account.

Most Windows Phones also come with SkyDrive preinstalled, with users signed up via the account they use to get their phone started.

In addition to the automatic sign-ups, Microsoft has widely integrated SkyDrive so that it may reel in some people who could use it for a one-time file transfer or more.

For instance, even before shutting off Hotmail for Outlook, Microsoft had integrated SkyDrive with the email service. Early last year Microsoft said that 15 percent of all email attachments sent via Hotmail were first uploaded to SkyDrive, so it picked up some solid usage there.

SkyDrive apps are also available on iOS and Android devices.

Still, I'm curious to know how many people proactively sign up via mobile apps or on their computers compared to those who were automatically signed up and may hardly use the service. I asked Microsoft, but a spokeswoman said the company had nothing more to offer beyond the blog post.

More impressive to me are services like Dropbox, which late last year passed the 100 million user mark. Those users all sign up proactively.

The SkyDrive integrations with Office 365 and other products make it very easy to use and could make it popular. But services like Dropbox are making similar integrations, like the deal with Yahoo that makes it easy to store email attachments in Dropbox. It could be that Dropbox has enough of a head start with active users so that it will maintain its popularity.

Nancy Gohring is a freelance journalist who has been writing about mobile networks, cloud computing, and consumer electronics for more than a decade. Read Nancy's bio.

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