But IBM will face pressure too. It would have a more powerful datacenter rival in a combined Oracle-Sun, which would sell a complete enterprise stack of hardware, operating system and infrastructure software -- something IBM alone had previously been able to offer.

Microsoft did not respond to a request for comment for this story. The company's CEO, Steve Ballmer, told reporters in Moscow Monday that he was "very surprised" by the merger news, according to Reuters.

"I need to think about it," he said.