Much has been written about Open Office and about MS’s OOXML and the battle for open file format’s. However it looks as if Sharepoint could be a bigger threat than any of these.
MS is pushing Sharepoint through its channel partners as an ongoing revenue stream and Ballmer calls it ‘The next big operating system’. MS may be struggling with file format lock-in but Sharepoint is Content Lock-In and it doesn’t matter what the underlying files in the store are if MS holds the key to the proprietary storage then the file type is irrelevant. Sharepoint needs Windows to work, and MSSQL server to work, and IIS to work and Office to work so once Sharepoint get embedded everything else is sucked through automatically, hence the revenue stream to MS and to Partners. There are open source alternatives such as Magnolia and Alfresco that put the customer in control by using open standards repositories.
As Matt Assay says in his conclusion “But one way or another, proprietary and open-source companies need an answer to SharePoint. Small wonder, then, that Oracle has been building out its content management capabilities, as have IBM and others. Content is the center of the enterprise ecosystem, when all is said and done. SharePoint is Microsoft’s answer for controlling the next decade of IT”
Above gleaned from various articles as well as my experience installing and programming Sharepoint see Mary jo Foley at ZDNet for starters.