Actually most places it is more difficult to discover who killed someone and gain a conviction without a body. There is at least one example in the Netherlands of a murder conviction without a body, but heck no reason to have facts on one of these threads.
BTW, remind me, exactly home many days after the murder of Lacy Peterson was Scott Peterson walking around free? They have jailed a suspect with little evidence in this case. They seem ahead of the CA authorities, but do they have the right guy?
IIRC, the case of conviction w/o a body occurred because the perp confessed. I heard about the case you speak of on FoxNews a week or so ago in an interview with a Dutch lawyer. The suspect in Natalee's case certainly is not going to confess.
I don't recall how long it was exactly the Peterson was walking around after killing Lacy.. but 62 days seems to ring a bell. However, cold, land-locked SF Bay is entirely different from warm, tropical Aruba. A body will degrade much quicker in 80 degree water than it will in 60 degree water; the ocean off Aruba gets really deep really quick; and there is much more marine life in tropical waters than there is in SF Bay - meaning that the remains have most likely been eaten.
As to the jailed suspect, the law there allows them to keep a person in jail almost indefinitely if there is a flight risk, while the investigation is ongoing.