Ok so correct me if I miss one.
CF, SD, SM, MMC, XD, RS-MMC, miniSD, MS, MS pro, MG, MG pro, ATA and of course MS duo. All make up the complex, confusing and nightmare eco-system of Flash memory.
I personally think Sony memory stick is the worst of all of them with 4 different types of Flash memory formats which seem largely incompatable with each other. The licencing also keeps Memory Stick(s) prices quite high and I believe there are only 4-6 makers which can actually legally make them. I like what Sony do sometimes (psp and playstation) but come on now, its time to let go of memory stick and let the market decide. Ok enough about Memory stick for now. MMC, ghezz dont start me off. Why didnt it just merge into SD? MMC looks the same, acts the same but has odd voltages which dont work with certain devices, SD just works plus it has IO capbilities. Honestly I dont care if its called SD or MMC but they should have sorted it out before the mini's were produced. MiniSD fits smoothly into SD but is the true of Reduced sized MMC? I've not seen any sign of such a smooth interchange. Oh well, at least Smart media is slowly going away but the very odd xD has replaced it. I dont know why xD is around, what advantage does it have over SD and MMC? Lower voltage? What's the point?
On a positive finishing, Flash memory is getting really cheap now. 1gig SD and CF is about 35 pounds now and USB thumb drives are really becoming ubiquious. The 4 gig Flash memory in the ipod nano sounds like a lot now, but Samsung have already showed off 4x the space (16gig). With all this in mind, 2-4gig could be just around the corner but I assume other formats are also just around the corner too. Some suggestions for new names. xD nano, SD micro, SD-MMC, Mini Micro MMC, reduced micro sized SD, Memory stick super duo magic gate pro. Nahh, it will never catch on.