Why does Snape like Malfoy???

[laoisecronin at yahoo.com]

No: HPFGUIDX 28187

 I'm new at this so i'm sorry if i get anything wrong!
  i've just been re-reading ps/ss and i noticed that it says numerous 
times that Malfoy was Snapes favorite student!why?
 Snape was a death eater so he must know that Malfoy's father is one 
too. If Snape has come over to the other side surely he would know al 
l the things that the Malfoy family did during Voldemorts reign. If 
Snape was now "good" wouldn't he dislike malfoy a little bit for 
this, i'm not saying he should hate him for what his father has done 
but he certainly wouldn't be his favourite student!
 Or maybe Snape is just pretending to like him to divert attention! 
 Any thoughts????