Low IO count, and limited clock speed. It's also unsuitable if you want to keep your design private. Basically, the way this works is that all the different de

Low IO count, and limited clock speed. It's also unsuitable if you want to keep your design private. Basically, the way this works is that all the different designs are placed on a single chip, with address pins to connect your design to the io pins. This means that everyone participating will have access to all functionality. You essentially buy a single tile in a shared chip. This is also why it can be done so cheaply. Making 500 copies of 1 chip is way easier than 1 copy each of 500 different chips.