Apparently carrageenan is extracted from the sea vegetable called Irish Moss. Many raw food restaurants are now using irish moss powder for thickening raw food dishes (Ie Jubb's in NYC).

Like many things it's like the heavily processing, heat and chemicals required to take a natural product and turn it into carrageenan that result in it being considered less than healthy. It could also be due to the fact that it's usually used to thicken milk, another irritant to people with digestive problems.

Who knows!
Sheryl