It's been reported over at TGDaily that Micron plan to release the world's first *16GB* DDR2 module by the end of the year, these of course focused on the server market however. These modules will use a twin-die 36x2x2Gb stack arrangement and are expected to carry a humongous price tag of somewhere between $14,400 and $21,600 PER module :O
Servers memory capacity will get a boost later this year with availability of 16 GB modules. Micron is currently sampling the devices, which are built in a 36x2x2Gb "twin-die" stack configuration. Commercial availability is planned for late 2006.
Ultra-dense DDR and DDR2 memory modules ar etypically used in high-end server environments when a memory upgrade makes more economical sense than replacing a complete server. However, high-end memory is not quite mainstream in terms of pricing and typically out of reach for the average customer.