Via Bruce Schneier, it seems the assassins might not have botched anything. And you know all those CCTVs in London? More evidence they're completely useless:
It has been more than eight months since the murder of top Hamas official Mahmoud al-Mabhouh, whose body was found in a Dubai hotel room Jan. 20. Quick work by Dubai police and a diplomatic furor over the use of dozens of forged passports in the case fed early optimism that at least some of the 30-plus suspects would be found. But a string of apparent dead ends has frustrated international investigators, lengthening the odds that anyone will be caught or that definitive proof of Mossad involvement will emerge.
And despite an initial burst of tough talk from various governments, some international investigators are concerned that politics may be hampering cooperation from some governments that support Israel.
... Police spent about 10,000 hours poring over footage from some 1,500 security cameras around Dubai. Using face-recognition software, electronic-payment records, receipts and interviews with taxi drivers and hotel staff, they put together a list of suspects and publicized it.
As Schneier has said, if the police spend resources on CCTVs and other high-tech options, they don't have those resources to spend on footwork.