For women who have frizzy hair, silicone hair products are a godsend. They seem to add shine, silkiness and manageability to hair that needs taming. And when you straighten your hair, it helps add that pretty sheen to it. But are these "serums," as they're sometimes labeled, aren't all they're cracked up to be. If you're in the market for something that smoothes flyaways, tames frizz and keeps hair in place,...