Actually been considering Janrain for some time.
But I realised that a lot of our customers (aged between 35-55) are not comfortable associating social tools with checkout processes.
(This information was achieved through questions asked to about 30-40 customers).
Eventually decided not to use this during the checkout and registration process.
Also found a discussion about this:
http://stackoverflow.com/questions/655710/is-openid-necessarily-a-good-choice-for-ecommerce
If you cater for a young demographic, then you should use this, as the younger generation take security for granted. Older generation do not (unless they are techies!)