I think it's about time rechargeable lithium-ion batteries got some size and voltage standards for use in portable electronics. Most of the mid-to-high-end stuff we buy in that space runs on these rechargeable batteries, all custom-designed by the manufacturers. You'll have a hard time convincing Nokia or Nintendo to go with a standard 5 Volt, Size 4 battery for phones and the next portable game console, mostly because of their replacement battery market and the fact that it makes their designs harder to modify, but it seems silly to throw out electronics once a year just because the battery can't hold a charge any more.
Mokalus of Borg
PS - And if battery technology improves, the standard sizes can still be used.
PPS - That's been happening with AA and AAA batteries for a long time now.