It seems inconceivable to me that Syria would conduct such an operation given the unsettling air that continues to follow UN Res 1559 (and the latest threats in Bush's speeches and Condi's rhetoric). Syria has consistently tried to build bridges with the US and offer peace initiatives towards the Israelis since 9/11. All they received in return is insults, misrepresentative, military attacks, sanctions (SALSA) and UN security council resolutions against it.
Hariri was never anti-Syrian although obviously not in the pocket of the Syrian's (like other Lebanese politicians). He and Damascus seemed to always have very pragmatic relations of mutual benefit. Hariri was instrumental with his contacts in Saudi, the Gulf, and France when Bashar was being groomed pre-2000. I took Bashar's quick appearance and statements as those characterized by a surprised and disorganized response than anything more calculated. Hariri rebuilt Beirut and Syria was a key economic partner in this project. Hariri was a compromiser. The Syrians are not going to assassinate him over speculation that he was going to openly go opposition. Besides such a bold, change in style seems an unlikely move politically in any arena. As one of my better connected contacts in Lebanon and Syria argued via email to me "Hariri never crossed the Syrians anyways....And he was very on the fence about the proposed pullout."
That said - there are rumors circulating already. There is something about Hariri potentially allying with Jomblat in the upcoming May elections. That may be all the motive the Western press needs. Naturally the Western media are going to argue this all happened under Syrian occupation (or the mukhaberat's watch). So basically the Syrians did it or they knew about it or their presence created a climate that fosters such assassinations. Particularly the latter reflects the white house's view (via the McCellan briefing) and is a logic leap. The Bush admin has gone to great lengths to argue that 9/11 was not their fault - its was Clinton's - even though it happened on their watch. So that logic that it happened because of Syrian occupation is ideological and unrepresentative.
Syria would have not conducted such a risky operation or tacitly let it happen in the hopes of showing that their Lebanese presence is still required. Syrian occupation of Lebanon is unlike the other two occupations in the region. It is more rooted in politics and economics and less on the military.
Perhaps, I will be proven wrong. If that ends up being the case, fine, I can admit when I am mistakenly analyzing something. But I am not going to rush to the western press's conclusions that Syria's invisible hand is responsible until I am shown some sort of link.