They will quote something they read on another forum or something someone told them as if they they just did the job themselves. Before taking any notice of such people ask them to prove their theories, it will soon go quiet.
An armchair theorist porting and polishing his tailpipe whilst filling up with hot air yesterday:
Hmmm, nothing really floating my boat recently music-wise so lets go back in time with a classic just for the Keyboard Warrior:
http://www.youtube.com/watch?v=1g09GzbctlA
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