The iPad has a lot of apps, but if there's a glaring hole, it's the absence of Microsoft Office.
Although there have been reports that Microsoft has built an iPad version of its Office suite of programs, the Redmond, Wash., company has yet to release them. Those programs would include Microsoft Word, Excel and PowerPoint.
So how much is Microsoft leaving on the table by not placing Office on the iPad? About $2.5 billion a year, estimates Morgan Stanley analyst Adam Holt.
In a note sent to investors, Holt said he calculates that if Microsoft released Office for the iPad, as many as 30% of iPad users would buy the software, according to a report by AllThingsD. If that number swelled to about 200 million in 2014, Microsoft would make $2.5 billion -- and that's after Apple takes its 30% cut for selling the app on the App Store. That also doesn't account for how much Office for the iPhone and iPod Touch could generate.