I have 3 main questions about the algorithms in intelligent web (web 2.0)

Here the book I'm reading http://www.amazon.com/Algorithms-Intelligent-Web-Haralambos-Marmanis/dp/1933988665 and I want to learn the algorithms in deeper

1. People You may follow (Twitter)

How can one determine the nearest result to my requests ? Data mining? which algorithms?

2. How you’re connected feature (Linkedin)

Simply algorithm works like that. It draws the path between two nodes let say between Me and the other person is C. Me -> A, B -> A connections -> C . It is not any brute force algorithms or any other like graph algorithms :)

3. Similar to you (Twitter, Facebook) This algorithms is similar to 1. Does it simply work the max(count) friend in common (facebook) or the max(count) follower in Twitter? or any other algorithms they implement? I think the second part is true because running the loop

 dict{count, person}
 for person in contacts:
        dict.add(count(common(person)))
 return dict(max)

is a silly act in every refreshing page.

4. Did you mean (Google) I know that they may implement it with phonetic algorithm http://en.wikipedia.org/wiki/Phonetic_algorithm simply soundex http://en.wikipedia.org/wiki/Soundex and here is the Google VP of Engineering and CIO Douglas Merrill speak http://www.youtube.com/watch?v=syKY8CrHkck#t=22m03s

What about first 3 questions? Any ideas are welcome !

Thanks