@ Frituurman
Good point, Sony and Philips engineered the hugely successfull Compact Disc (CD) and was meant to replace the LP records and with regard to Sony's MiniDisc, Philips and Sony rather meant to replace Philips' music cassettes, instead the Compact Disc seems to have virtually replaced both.
Surely the Compact Disc format has been a huge success and likewise were Sony's introduction of 3.5 inch diskettes.
BTW, IMO UMD hasn't failed at all. AFAIK UMD disc production is still increasing. Looks like an excellent storage media for the PSP, don't get me wrong I like the cartridges for our Nintendo DSes as well, but for the types of games available for the PSP tend to require much more storage, UMD seems more suitable to me.
I find it's funny people are calling Blu-Ray to be solely Sony's format though, there's a huge consortium behind this format.