Flame retardants are added to many of the products we purchase. It is mandated by law. I would be surprised if anyone on the board who has purchased a couch in the last twenty years has one without flame retardants in the cushions. Manufacturers are required to put them in childrens sleepware. You, as a private citizen are not required to do so.
I prefer to use materials that do not contain the flame retardants. I wish I could purchase furniture without them. They are toxic, and I think it's debatable how helpful they really have been. Studies have shown PBDE's (one very common class of flame retardant) showing up in breast milk, which isn't surprising considering the toxic load that we all carry in our bodies.
Sorry, off my high horse now...I wouldn't use them unless you really want to. I can't imagine why you would want to, though, unless your grandchild plays with matches.