Here are a few ideas gathered from reading again many very interesting posts.

Listed below are a few of the reasons posted for not adding all of the requests received, to one's friends list.

1. They have never commented on my blog.
2. They write in another language.
3. They are only advertising something.
4. Upon reading their blog, I found it not to my liking.
5. I never read their blog previously.
6. Their blogs are impersonal, they just print articles.

This list might be worthwhile considering, especially if you are receiving 'be my friend requests' from those who are clearly strangers to you. Of course you may be lucky and have never been faced with this situation.