Interesting story here on The Register

http://www.theregister.co.uk/2006/02/16/megasim_launch/

"The device on show today was not just vastly bigger in terms of capacity at 512 megabytes (compared with 16 or 32 kilobytes free on a 64 kilobyte chip, for standard SIMS) but is also faster, running at 20 megabits a second, instead of the usual 9.6 to 128 kilobits per second of the normal config chip. Ultimate capacity is "whatever the technology provides", Ira Cohen, VP marketing of the company said."