IBM Patent Benevolence?

Doc comments with grudging admiration that IBM has decided to give away __ some parts of their much vaunted patent portfolio. One interesting tidbit is that in addition to being responsible for the most patents granted annually, IBM is also the leader in the most patents allowed to expire annually. Why? Because keeping all those patents current is very costly , and if there is no economic benefit to having those patents, that's a lot of money down the shute. So maybe some clever strategist/marketer (difference?) probably realized that the PR value of open sourcing these worthless patents might actually be the most valuable of all!