According to reports apparently originating at 9to5Mac, PhotoFast has complied with a request from Apple to stop production of the device.
9to5Mac suggested that PhotoFast went along with Apple's request because it did not want to harm its iPad/iPhone accessories business. The company is a participant in Apple's MFi licensing program which (among other things) provides access to the proprietary connector and other components needed to make accessories for the iPod, iPhone and iPad.
But what does Apple stand to gain? It does not offer a 256GB storage option for the 11in MacBook Air, only on the 13in model. Surely the main attraction of the 11in model is its compact dimensions, so potential buyers are unlikely to select a 13in configuration just for the extra storage.
From that perspective, arbitrarily blocking the PhotoFast kit hurts Apple.
What's the alternative? See page 2.
If that is the case, it could just be a matter of negotiating an acceptable royalty (as with the dock connector). Alternatively, Apple's plan could be to deny access to the connector to everyone apart from its own suppliers (as with MagSafe).
People do expect to be able to upgrade the storage in laptop computers, so the latter course could harm sales of the MacBook Air, however much Apple - and, by many accounts, especially Steve Jobs - seems to favour a 'sealed box' design for its products.