Yes. Today's comic really is about different intentions. People usually have some sort of motive to be your friend or to talk to you. It's only normal. I've taken it for granted nowadays. Everytime friendliness comes around it's got to have a reason. But I think that sometimes its okay not to take it too hard. It always is good to kindly accept the good and giving some back by being friendly.
Of course, one still has to be careful not to have to pay dearly for it. I remember this one time when I was approached by a friend from school. I haven't had a chat with him in a while so I thought I'd be a nice guy and be friendly. Apparently he then put his arm over my shoulder, making me think he wanted to pull out a joke or say some pun to cheer me up. Instead, he asked me for a favor. We had a test and he got really crap marks and was afraid his parents would see it. So he decided to ask for mine, change the name on it and show it to his parents. It seemed like an act of mercy at first, but I declined. It seemed, with him honesty wasn't the best policy and it would suck if I was going to be cheated the same way in return in the future. I told him to apologize to his parents and promise to do better next time. Whether he did it or not is another question.
So make sure, you stay an angel, but don't let anyone take advantage of you. It's always your call. Just depends on whether you realize it or not.