Edison's dimming bulbs. [1] An interesting piece from Slate on consumers and the gradual move from incandescent to CFL technology, and the role governments and retailers are playing in this migration.

... while they've grown in popularity, CFLs have yet to emerge as a household staple, in part because consumers can't see beyond the shock of the sticker price to the long-term savings. "When you buy a compact fluorescent bulb at the cash register, you experience the higher cost vividly and all at once," says Robert Frank, a Cornell economist and author of The Economic Naturalist. "But when your electric bill goes down as a result, the savings are not as evident." Consumers routinely make such short-term economically irrational decisions.