When there are no new updates on a case, people fill the void with theories. The assumption seems to be that the lack of obvious progress from the police means that the crime committed must have been much more complex or unusual than it first seemed. Often these theories involve bizarre conspiracies and unusual motives - trafficking, gangs, etc. However, when the cases are finally solved, most will turn out to be relatively simple. Unfortunately some criminals are either very effective at hiding their crimes or just simply lucky.
That's why I mentioned McCann.
According to the Daily Mail, with a holiday resort crawling with burglars, gypsies, eastern european baby smugglers, childless women who look like Victoria Beckham and pedos all staking out the apartment in suspicious getup its amazing one didn't drive straight back to the airport!
LOL
But yeah - probably a far simpler explanation.
ETA - i don't care about the case - just the absurd daily mail style theories