Why do strangers avoid me? Is this normal?

I had a lot of strange people I didn't know adding me to msn in response to a personal classifieds ad that I posted but most of them delete me as soon as they realize our interests are not compatible. Second degree friends that I have that I meet through other people reject me as a friend on facebook and so do fellow classmates that I haven't seen in more than three years. Why is this? Also when I go to the christian fellowship in my university and ask people for their e-mail addresses, they always say no and a lot of people just avoid having any contact with me. and move to another table when I sit where they are. I don't know why so many strangers are avoiding me. Is this normal?
Why do strangers avoid me? Is this normal?
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