Here are some negative reactions, and the mention of 'Carbon Credit' sales as a motive
http://www.eurekalert.org/pub_releases/2007-06/wwf-wwf062707.php
“There are much safer and proven ways of preventing or lowering carbon dioxide levels than dumping iron into the ocean,” said Dr. Lara Hansen, chief scientist, WWF International Climate Change Program. “This kind of experimentation with disregard for marine life and the lives of people who rely on the sea is unacceptable.”
Planktos, Inc.— a for-profit company — will dump up to 100 tons of iron dust this month in a 36 square mile area located approximately 350 miles west of the Galapagos Islands. Planktos, Inc. plans to dump the iron in inter...

Here are some negative reactions, and the mention of 'Carbon Credit' sales as a motive
http://www.eurekalert.org/pub_releases/2007-06/wwf-wwf062707.php
“There are much safer and proven ways of preventing or lowering carbon dioxide levels than dumping iron into the ocean,” said Dr. Lara Hansen, chief scientist, WWF International Climate Change Program. “This kind of experimentation with disregard for marine life and the lives of people who rely on the sea is unacceptable.”
Planktos, Inc.— a for-profit company — will dump up to 100 tons of iron dust this month in a 36 square mile area located approximately 350 miles west of the Galapagos Islands. Planktos, Inc. plans to dump the iron in international waters using vessels neither flagged under the United States nor leaving from the United States so U.S. regulations such as the U.S. Ocean Dumping Act do not apply and details do not need to be disclosed to U.S. entities.
“World Wildlife Fund’s concern extends beyond the impact on individual species and extends to the changes that this dumping may cause in the interaction of species, affecting the entire ecosystem,” said Dr. Sallie Chisholm, microbiologist, MIT and board member, World Wildlife Fund. “There’s a real risk that this experiment may cause a domino effect through the food chain.”

http://www.grist.org/news/daily/2007/06/19/4/index.html
The company, Planktos, will use the iron to spur the growth of phytoplankton, which can absorb carbon dioxide. It would then sell carbon credits based on the project. Critics have pointed out a boatload of flaws with the plan, including the fact that the plants can release other greenhouse gases when they decompose. Now the EPA says the release of nearly 50 tons of iron requires a permit under the Ocean Dumping Act. The International Maritime Organization will consider the topic at a meeting this week; says Ken Caldeira of the Carnegie Institution: "It's far-fetched to claim you help ocean ecosystems by disturbing them."