Here is a nicely made video about reading difficulty with a number of famous people talking about their own experiences:
http://www.youtube.com/watch?v=8m1fCz3ohMw&feature=share
As you listen to it you will see lots of examples of the 7 causes of difficulty that we identify routinely:
http://www.easyreadsystem.com/info/dyslexia.html
Almost certainly all of them could have learned to read well with the right support, but there you go.