Apple's new MacBook Airs come with a fancy new type of SSD drive developed and built by Toshiba. They look like RAM sticks with a mini-PCI-esque connector on one side. They are somewhat user-replaceable, and as such, PhotoFast got clever and offered a faster and more spacious alternative for those not worried of voiding their warranty.
PhotoFast's SSD drives are available with 256GB of space, and run at 250 MB/s - as opposed to Apple's 150-160 MB/s. In a move that I personally found to be rolling in awesomeness, they also offered a kit that let you turn Apple's slower SSD into a USB drive.
Well, Apple wasn't pleased with this, and asked PhotoFast to cease production of their replacement drives. The Taiwanese company complied because they are afraid they might otherwise be kicked out of Apple's MFi licensing program, which allows PhotoFast to build licensed accessories for some Apple products.
The reason for Apple's cease and desist isn't clear at this point, but most likely there's either an IP issue involved, or there's an agreement between Apple and Toshiba which gives exclusivity to Apple for the time being - Toshiba will be offering the design to OEMs shortly. Of course, Apple will probably offer faster SSDs in the next MacBook Airs, and can't have PhotoFast running around in the meantime.