So one good rocking kick and blamo..its open, thats the major flaw in the door...go take a look at your front door...nice heavy deadbolt in the hole, and about 3/4" wood on either side
http://www.wikihow.com/Kick-Down-a-Door Oh and look a wonderful "HOWTO"
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A good strike plate is the way to go
http://www.thenationallocksmith.com/public.asp?2
So much for the fear of "no knock" warrants or the determined home invader