Recent large ships taken by pirates:

Pirates seize Japanese cargo ship off Somalia

No word on 23 crew aboard; attack comes despite increased security

The Associated Press
updated 12:08 a.m. CT, Sun., Nov. 16, 2008

And:

Somali pirates seize supertanker

Hijackers sail Saudi-owned vessel — the largest ever taken — to Somalia
The Associated Press
updated 2:05 p.m. CT, Mon., Nov. 17, 2008

This second one, the one cited at the beginning of the thread, is the largest vessel (thus far) hijacked, and was attacked about 450 miles out in the open ocean.

DUBAI, United Arab Emirates - Somali pirates hijacked a Saudi supertanker with a cargo of crude oil hundreds of miles out in the Indian Ocean in a dramatic escalation that showed their expanding reach.

Many smaller vessels are attacked, frequently with crews and vessels held for long times, and fairly often with the murder of crew members.

From the first link, a summary of causes and conditions:

Somalia, which has had no functioning government since 1991, is the world's top piracy hotspot. It is located along the Gulf of Aden, which connects the Red Sea and the Indian Ocean and is one of the world's busiest waterways with some 20,000 ships passing through it each year.

Somali pirates are trained fighters, often dressed in military fatigues, using speed boats equipped with satellite phones and GPS equipment. They are typically armed with automatic weapons, anti-tank rockets launchers and various types of grenades.

In October, 22 sailors — eight South Koreans and 14 citizens of Myanmar — were released following a month of captivity after their South Korean shipping company paid a ransom to Somali pirates.

South Korea has said it is considering dispatching navy vessels to waters off Somalia to fight rampant piracy.

NATO has sent three ships to the Gulf of Aden to help the U.S. Navy in anti-piracy patrols and to escort cargo vessels.

The European Union has said at least four warships backed by aircraft will begin policing the dangerous waters in December. The EU flotilla will eventually take over the NATO patrols.

Despite the increased security, attacks have continued unabated off Somalia. There have been more than 80 attacks this year in the African waters.

From the second link:

Pirate attacks off Somalia have surged more than 75 percent this year, hitting freighters, tankers, yachts and fishing vessels. The pirates raised international alarm bells in September when they seized a Ukrainian freighter, the Faina, carrying a cargo of battle tanks and other weapons. The Faina and its 20-member crew are still being held off Somalia, watched by warships to prevent the removal of its cargo.

With most attacks ending with million-dollar payouts, piracy is considered the biggest economy in Somalia, a country that has had no stable government for decades. A report last month by a London-based think tank said pirates have raked in up to $30 million in ransoms this year alone.

***

The seizure of the Faina and its cargo of weapons prompted a reinforcement of warships patrolling the waters off Somalia. Along with a Russian frigate and Indian vessels, a NATO flotilla of seven ships is in the Gulf of Aden to help the U.S. 5th Fleet in anti-piracy patrols and to escort cargo vessels. The 5th Fleet said it has repelled about two dozen pirate attacks since Aug. 22 in the gulf.

Another multinational fleet currently led by the Dutch has carved out a protected lane through the Gulf of Aden, through which 20,000 tankers, freighters and merchant vessels transit every year, entering and exiting the Suez Canal.

But other ships — including ones too big for the canal like the Sirius Star — pass off East Africa to circle the continent by the Cape of Good Hope.

The expansion of attacks signals they too could be vulnerable.
"There will never be enough warships," said Graeme Gibbon Brooks, the managing director of British company Dryad Maritime Intelligence Service Ltd. "The whole area is 2.5 million square miles ... the coalition have to act preemptively and be one step ahead of the pirates."

John