I notice that alot of people cover the name of the person they played against when posting a game... why is that? I understand if you are going to rip holes in their play then MAYBE it would be more polite to not expose who you are accusing of poor play.

 However, if the game was played on this site it is viewable to the public anyway.  And more than that not having someones name attached to the game seems to make it more likely for people to be mean when analysing the game. 

Is there some other reason why people don't post the names of the opponent?

some people have pride and/or dignity. I have none