'The argument from personal experience is the one
that is most convincing to those who claim to have had one.
But it is the least convincing to anyone else, especially
anyone knowledgeable about psychology.

Many people believe in God because they believe they have
seen a vision of him - or of an angel or a virgin in blue - with
their own eyes. Or he speaks to them inside their heads.

You say you have experienced God directly? Well, some people
have experienced a pink elephant, but that probably doesn't impress you.

Peter Sutcliffe, the Yorkshire Ripper, distinctly heard
the voice of Jesus telling him to kill women, and he was
locked up for life. George W. Bush says that God told
 him to invade Iraq (a pity God didn't vouchsafe him a
revelation that there were no weapons of mass destruction).
Individuals in asylums think they are Napoleon or Charlie
Chaplin, or that the entire world is conspiring against them,
or that they can broadcast their thoughts into other people's
heads. We humour them but don't take their internally
revealed beliefs seriously, mostly because not many people
share them.

Religious experiences are different only in that the people
who claim them are numerous. Sam Harris was not being
overly cynical when he wrote, in The End of Faith:
"We have names for people who have many beliefs for which
there is no rational justification. When their beliefs are extremely
common we call them 'religious'; otherwise, they are likely to
be called 'mad', 'psychotic' or ' delusional'...
Clearly there is sanity in numbers. And yet, it is merely an accident
of history that it is considered normal in our society to
believe that the Creator of the universe can hear your
thoughts, while it is demonstrative of mental illness to
believe that he is communicating with you by having the
rain tap in Morse code on your bedroom window.
And so, while religious people are not generally mad, their
core beliefs absolutely are."  '

Full article at:
http://www.timesonline.co.uk/article/0,,564-2428935.html