User blog comment:D. Cello/Assassinews 10/11 -- Desmond's Ancestry Revealed/@comment-187.40.70.98-20111015161254/@comment-94.212.221.48-20111015204338

Not everyone is able to use it, only the crossbreed people (the real assassins). Just like these crossbreed have somesort of thing in their head (I forgot the name :P) which makes 'em able to use POE's but aren't affected by them either. (example: Rodrigo Borgia trying to use the Apple & co.)