Why singleton is bad

- Against the OO spirit and increase coupling which usually becomes hidden

- Classic Singleton approach is hard to unit test

- Classic Singleton Class is hard to be inherited

http://code.google.com/p/google-singleton-detector/wiki/WhySingletonsAreControversial

http://stackoverflow.com/questions/1020312/are-singletons-really-that-bad

http://misko.hevery.com/2008/08/17/singletons-are-pathological-liars/

http://misko.hevery.com/2008/08/21/where-have-all-the-singletons-gone/

http://sites.google.com/site/steveyegge2/singleton-considered-stupid