I read labels and avoid it if I can. It's hard to find some dairy products that don't have it -- for instance, most buttermilk does.
InSoFla, I know the powdered formula we use for my daughter does not have carrageenan. I was curious, though, so did some looking at three other brands. None of the powdered formulas contained it, and only one of the liquid formulations did. The great majority of babies on formula get the powdered stuff, so there's that, at least.
ETA that I think it makes the texture of stuff gross. Like I said, it's in a lot of dairy products. I accidentally got some sour cream that had it, and it had a really terrible gloppy texture. Same goes for cottage cheese that has it. Ick.