It meant deleting things you can't usually delete from your phone using a PC application so you get more application space. I do it on older phones for friends when app space is limited i.e when someone has a curve 9300 on OS 6 and very little free application space, shrinking helps there. I did it on my Bold 9000 too so it can run smoother. But if you delete languages and apps you don't seed on your 9930 you won't really need to shrink your OS, newer devices don't rely on it to run smoothly, people just do it as they have done before and it has become habit and something they enjoy doing.