Two days ago my wall on Facebook changed, the link facility to have either top stories or most recent stories has gone and I cannot change between the two, does anyone have any idea how I can get it back to how it was?
It might have something to do with the changes facebook is planning for the way news feed is presented to the user.
Now Facebook engineers are working to create an unfiltered News Feed that would open the floodgates of information about users and the games they win, the companies they "Like" and the actions their friends take, said people familiar with the matter.
From here (it's a google redirect to a behind-pay-wall WSJ article).
You cannot change it back. Top stories and most recent stories are now combined into a single unified News Feed. You also have more control over which stories are classified as "Top Stories" by clicking on the upper left corner of the story. These Top Stories will initially be displayed at the top of your News Feed, so if you haven't visited in a while they will not be buried under several pages of more mundane posts.
More details can be found in this Facebook blog post.