That's pretty much a proof Microsoft paid for it when Sony say it themselves.

Comic time (hint: Shiva the Motorycle):

"Sony's Tretton: 'Disappointed' In Multiplatform FFXIII Through MS' 'Currying Favor' Speaking at a roundtable Q&A attended by Gamasutra, Sony's Jack Tretton has been discussing Final Fantasy XIII's move from a PlayStation 3 exclusive to a multiplatform title, suggesting Microsoft has spent most of their money "trying to curry favor with third parties".

When asked whether he was disappointed about the surprise announcement that the game would also debut on Xbox 360 in the West, Tretton noted: "I guess disappointed is clearly an appropriate term."

Tretton then launched into invective discussing Sony's decision to concentrate heavily on internal development, noting that it constituted "over half of our employee base all over the world", and adding that "...we've built up our base and that's where we've chosen to spend our dollars."

However, he warned: "I think Microsoft has spent the majority of their money on trying to curry favor with third parties" - implying that Final Fantasy XIII moving to multiplatform was more of a Microsoft-subsidized decision than one guided purely by sales reasons.

Tretton concluded: "I think software companies look and say 'there's no check big enough for us to do exclusive development' ...I think it's going to be harder and harder to have third-party exclusives as we move forward."

Gamasutra will have more from Tretton's roundtable Q&A in the near future, including lots more detail on the state of Sony."

http://www.gamasutra.com/php-bin/news_index.php?story=19448

Looks like they really were suprised by this announcement.

Yes and no ...

Right now that strategy will work amazingly well for Nintendo. They have massive revenues, low costs, low development costs, massive cash supply (they're building a money-bin to swim in) and solid sales which means that they can buy just about any developer they desire and fund their development without worrying about whether these games are successful or not. This may not sound like a massive advantage, but it is easier to develop talent while working on smaller projects that do not need to be released on time or to be successful than it is when they're working on larger projects that need to be released on a strict schedule, sell well and sell systems.

It still will be a good strategy for them, but Sony also needs the big titles to sell more systems in order to have the userbase to support their massive development costs.