Absolutely. Everyone has a valid opinion and everyone has a reason for thinking the way that they do. You should always listen to what someone else has to say, you just might learn something. Without the opinions of others it is much harder to improve yourself and experience the things around you to their fullest extent. People are your greatest resource.
Depends on what it's about.. if it's there opinion on me no I really could careless do to the fact life is short and everyone should live it the way they want to because some people can't live at all because of there problems...