Rodney Brooks is the Panasonic Professor of Robotics at MIT and CTO of iRobot. From 1997 - 2003 and from 2003 - 2007, respectively, he was Director of the MIT Artificial Intelligence Lab and Director of the Computer Science and Artificial Intelligence Laboratory. He knows a lot about robots, AI and exponential growth curves.
During his talk at the Singularity Summit 2007, Professor Brooks give his prediction for the storage capacity of an iPod in 2025--40 million gigabytes or 40 petabytes, or room enough for more than 10 million super-high fidelity songs. For context, a Macintosh computer in 1985 has an 800 kilobyte floppy drive, and an iPod today 16 gigabytes.