Why are some shows cancelled so soon?

It's the Fall Season.  Some new shows have already been given the quick hook (sorry MADE IN JERSEY).  I Got a Friday Question about that that has turned into its own post/rant. 

Joseph Scarbrough posed it:

In the old days, a network would wait until the end of the inaugural run of a new series to determine its ratings, and whether or not the series would be renewed (in other words, if a