There's also the lack of interesting controversies to spur editors' interest in the Chilean earthquake. With Haiti, you had Pat Robertson's stupid comments, the alleged attempted kidnapping of orphans, the invasion of Scientology, etc. Haiti's geographic proximity also increased relative coverage. The US English language media also largely ignores Latin America unless Hugo Chavez says something to hurt our feelings.
Of course these theories only apply to US-based editors. It would be an interesting exercise to geographically map out IP addresses and see where the interest and lack of interest is coming from.