But why shouldn't Iran think that, that they can dick around with the West? After all, they've been sending Revolutionary Guards into Iraq and providing terrorists there with increasingly deadly weapons, basically with impunity for some time now (no doubt They were provided for peaceful purposes too, just like their nuclear program). Yeah ... the nuclear program ... that's been going on, with the UN ratcheting up the pressure from "mother, may I criticize you" to a stern chiding all the way to a harsh warning. And Tehran (rightly from their POV) laughs in its face.
It's not as though hostage-taking, specifically, has never worked for the Iranians. Practically the first act of the Islamic Revolution was to invade the U.S. (no hyperbole -- an embassy is sovereign territory under every international convention) and hold diplomats hostage for more than a year. Not only that, but this act was participated in by Iran's current president (according to plausibly sourced reports; here's a respectable partial dissent).
And that 1979 invasion of the US went essentially unpunished. The worst consequence Iran may have suffered was the (very) slight US tilt toward Saddam Hussein in the Iran-Iraq war (though the facts about the Saddam regime put a very firm ceiling on that for the US; less so for the humanitarian conscience-wielders in Paris and Brussels, not to speak of Moscow). A few choppers, a reel of satellite photographs and the veto of any UN condemnation of Saddam. Big whoop. The Iranian regime learned -- it can take hostages without serious consequence, and mess with the Great Satan and his little henchmen with impunity. (Do the moral equivalancers and "incentivizers" and appeasement-artists even remember things like how Iran's embassy in London was seized by Iraq-backed Sunni terrorists during its own invasion of the US and do they remember Britain's reaction thereto?) Their acolytes in Lebanon certainly learned the lesson, even the point of executing two US soldiers -- hanging one on tape; shooting another on a plane and dumping his body on the tarmac. How many Americans would even know those two men I'm referring to? There's no better proof of how deludedly self-forgetful we are with regard to the Islam that people with two brain cells think the Islamists hate us for any reason related to Dubya or Israel or the taping of Saddam's execution. The slightest familiarity with even contemporary history removes any excuse for believing such widely-held flatulence.
I think that cost-free 1979 Iranian invasion of the US was the biggest factor in emboldening the current wave of Islamism against the West. Not the causus belli from their POV, not at all. Rather, that because of what we did then (or didn't do), we gave them reason to have contempt for us. They hate us (that's a given, for reasons of their own); and we have given them no reason to fear us. Which is the worst of all worlds, since the mix of hatred and lack of fear produces contempt. The ignorant like to abuse Machiavelli, usually unread, but Chapter 17 of The Prince deals with this point very nicely:
Upon this a question arises: whether it be better to be loved than feared or feared than loved? It may be answered that one should wish to be both, but, because it is difficult to unite them in one person, is much safer to be feared than loved, when, of the two, either must be dispensed with.
In this case, one must be dispensed with since the Islamists will never love us. And since men love according to their own will but fear according to the will of others, we can only give them reason to fear us. Or not.