I want to see more on this before I make a decision on whether it's OK or bad. Time and time again, you hear about some sort of food or ingredient being horrible, then they come back and say that it has some sort of awesome benefit.
The key, in any case, is usually moderation. Or eat whole, unprocessed foods.
Here is an interesting discussion where both sides of the story are discussed. Read the main article, then skip down to the discussion.
Carrageenan Isn't Good For You: High Correlations to Cancer and Inflammation
Read the reply @ June 4, 2012 at 7:53 pm, and the further replies to that posting. Seriously, if this person is making food out of that same seaweed, then it has carrageenan in it. But the blogger goes on to tell him that it's OK if consumed as long as it's still part of the seaweed?
Then read the reply @ July 16, 2012 at 12:05 pm, and the further replies to that posting.
I don't think it's as simple as "all carageenan is bad for everyone." Sure, there could be some people that truly have a problem with it. Some people can't eat peanuts or gluten, etc.
But if you don't like the idea of it, don't eat it. Simply put, when it comes to food additives, eat whole foods and stay away from processed foods and your problem is solved. The amounts we are subjected to are probably very little anyway. I can't remember the last time I ate ice cream, and I do eat yogurt but it isn't in the yogurt that I buy. It isn't in any of my dog's food or treats, either.