Myspace has always allowed the selling of [and promotion of] apparel within it's community. Once they became the home of millions of indie bands and startup clothing companies, not only did they allow it, they encouraged it.
Music [digital or otherwise] however, was never allowed for sale until they figured out the SnoCap system and how to integrate it and make certain that the music for sale was being sold through the proper channels.
This whole thing is really nothing new, the actual "widget" may be new, but Paypal users have always had the option of writing their own code and creating Paypal "Buy Now" buttons which could be placed on Myspace [and Facebook, for the comment on the Paypal blog who said they needed one for Facebook]. To make the whole thing semi-automated, all you need is MS Excel and a base Paypal code to generate new listings from. You could make the pictures any size you want, add any features or options you want and have your whole inventory digitized in about 10 minutes of computer time [assuming you already have pictures of your items hosted online somewhere].
I had been doing this from 02/06 until 05/08 and sales have been moderate as compared to elsewhere. For the comment above who said they ran into trouble for "spamming" I see how that could happen and urge anyone who wants to do this to walk a fine line with their Myspace promotion. Posting to Myspace groups and posting bulletins on occassion is one thing, but if you post bulletins every hour and spam every group forum board with your self promotion, you may have the opposite effect of what you're trying to achieve. You could end up losing "friends" more rapidly then you are gaining them.
If anyone here is interested in this and needs help setting up the code or going through the procedure, then post your interest here. It's relatively easy to do [and free].