Speaking with GI.biz, Peter Edward - PlayStation Home's director - reckons that despite costing a bucket to develop, the priority with Home at the moment is not to make money. It's to build a community.
...our belief is that if you make the community happy, and get good content on to the platform, if you get a platform that people want to keep coming back to, then the monetisation aspect of it will almost take care of itself.
It's certainly not something that should be the driving force, not something that's the driving priority at this stage of development. We have to focus on making sure we're giving the community what they want, and making sure the platform itself is sufficiently capable and robust, and that the content is there. That's definitely our priority.
He's so right! If there's one thing I've learned about Home in my time, it's that the few things you can do in the service are in no way, shape or form a paid-for advertisement.