It may delight you to know... that I have no idea. I have been paying attention to the story, though what has surprised me more - perhaps by now it shouldn't - is the pathetic attempts at outrage and insistence on lawfare now spreading through the anti-Israel European community. That said, I have yet to see a single person shed a tear, or even waste a shrug on the news in the US. In addition, it apparently doesn't seem to bother the government of Dubai that known international terrorists are entering its borders to traffic in weapons with nearby rogue nation states with ambitions to dominate the region.
If this was Mossad, my utterly uninformed perspective is that using passports of Israelis with dual European citizenship, and having the entire operation captured on camera... it seems very sloppy. Having read By Way of Deception: the Making of a Mossad Officer in my youth, I happen to know that the legend of Mossad has long exceeded the organization's many successes, and surprisingly many failures. Still, one would expect... more.
Israel is a small country, with limited resources. There are only a handful of Mossad operatives trained in direct action, and to converge eleven or twelve such individuals on one target, in a hostile country - which is how Mossad defines Arab lands - to eliminate a murderer, yes, but who the hell was this guy? We're talking about a serious allocation of resources, with now a dozen burned agents, to deal with a mid-level weapons mule. Perhaps, or perhaps we're (or I am) missing something that made him a target of great importance. (In the comments, Tori suggests Mabhouh was the Hamas equivalent of Hezbollah's dearly departed Mughniyeh.)
But what do I know. Stratfor, on the other hand, I trust.
Regardless of who liquidated a terrorist murderer (with zero civilian casualties, for a change, bravo!), I'm interested to know how many people have been similarly murdered by American, French, British and Russian intelligence in the last six months. Actually, I take that back, I really don't care. I thought this is why spy agencies exist - to gather information and covertly kill people, when necessary. The only rule of spycraft is "don't get caught"; all else is fair game. This is an absurd non-story, and anyone who claims otherwise is a twit - a word I don't believe I've used before in written form, and which has a meaning, namely, "The kind of person that makes a retarded chimp look smart." (Hey, I didn't make it up, it's in the dictionary!)
I personally consider the leadership of Hamas to be dead men walking, and if I were in charge, I would not spare the bullets to send them all to hell. Them, and Samir Kuntar - an animal whose every gasp for breath is a stain on humanity.
Update: Dershowitz pontificates on the "extrajudicial killing" angle.