http://www.trustedreviews.com/article.aspx?art=2225
For those with short memories, single layer Blu-ray discs hold 25GB and relatively stable mass production of them has been around for a while now. The real technical challenge is to achieve the same results with dual, triple and quadruple layer discs which will boost potential capacities to 50, 75 and 100GB respectively. Sony even has a 200GB octuple (eight) layer disc in development, but that is some years away from the high street.