Ok, if seldom eaten. Instant noodles are not good for a person who has access to other healthier foods. Most instant noodles are high in fat and salt, and contain msg flavor enhancer (similar to eating potato chips with added msg). A few "healthier" instant noodles have less fat, less salt, and no msg; but the "healthier" noodles are hard to find in stores. It is better to eat noodles without using the flavor packet.
Yes and no. While instant noodles are not generally harmful (otherwise, they would not be sold), they may not be the best type of food to eat in that they contain quite a bit of preservatives (salt, for example) that may not be the best thing to consume for certain categories of people (such as those with elevated blood pressure). Definitely, some people may be allergic to some preservatives used in those.