3. He's having personal issues. A lot of women believe that no matter what a guy is going through if he likes them, he will show it. While this is definitely true most of the time, look back at your own life. Have you ever gone through a difficult time where you felt like you were carrying the weight of the world and taking care of yourself was exhausting, let alone dating someone else? We all have, including men. Maybe he's worried about losing his job, or is dealing with a family illness. Whatever the case, dating and being "polite" aren't at the front of his mind.
4. He's a player. For some men, dating is just a game and they are the MVP's. Once a player gets what he wants out of you whether that be your phone number or sex, he'll pull a disappearing act fast. He's not concerned with your feelings whatsoever.
5. He's scared. Have you ever considered that he's pulling away not because he doesn't like you, but because he likes you a lot? When a guy meets a woman who knocks him completely off his feet and catches him off guard with her intelligence, wit and beauty sometimes he doesn't know how to deal with it...so he runs. Men are so used to dating woman after woman that when they come face to face with someone special they tend to get a bit intimidated. Give him time to work through his feelings and if he knows what's good for him he won't let you slip through his fingers.