Iran taking 15 British soldiers hostage is Kellen Clemens throwing 2 touchdowns for the Jets when they are down 42-10 lat in the fourth quarter. Its just enough action to get the NY press buzzing about the possibility of him replacing Pennington, but it really doesn't mean shit. Pennigton is still the starter. Clemmens was going against a team that knew the game was over. They weren't throwing any blitzes at him, so he could basically stand there all day with no real pressure to perform but there is a ton of positive press that can be earned by throwing a couple of garbage time TD's. He had nothing to lose, and a ton to gain.
For Iran its basically the same way. If there were ever a fear of escalation, the prisoners would be released. The press they get is tremendous. You don't think Hugo Chavez is watching this and thinking "Damn, I wish I had done that". And that doesn't even count for the millions of Al Jazera subscribers who think that this is the greatest victory ever. Its is probably being sold as a direct assault on Britain who is still considered a super power and they're a huge US ally. So if Iran could take an opportunity to snatch up a couple of sailors and get some propaganda flowing, than they really have nothing to lose, its the 4th quarter and there down by 30.
Iran will eventually give up the hostages. It will take some time and some sort of persuasion, but they'll eventually get released.