Sose,
USB Ram stick so you can plug it into your USB port and upgrade your system's RAM?
If this is the general idea, forgive me but I do not see much of a market considering 4Gig memory is pretty much standard on any PC/Laptop these days. After than, you'll need to take in considerations the different memory types that exist for all computers. If the clocking of the USB RAM stick is not identical to that of your PC's RAM, it would most probably cause major performance degradation.
But even if you did manage to overcome all these issues, the bandwidth between the CPU and physical RAM would be much greater than that between the system and USB ram stick, so it would ultimately create bottlenecks.....
Anyone else who would like to join in ?