What is the number or percentage of golfers bit by snakes while golfing yearly?

Answering a question like this is impossible without investing much
time and work. You might want to have a look at the Google Answers
pricing guide:
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Do you want USA, some other country or world wide? If percentage
instead of number, do you want per 18 hole game or equivelent. Do you
want all kinds of snakes or only poisonous snakes.   Neil

Ah, the question suggests why Germans love to go to Ireland to play
golf;  they're deadly afraid of snakes and often playing in the deeper
rough.
It also suggests why cricket and not golf was the sport exported to the colonies.

Does being held in the embrace of python or boa constrictor count?

IF you would be satisfied with a percentage correct to only two
decimal points, I would venture to say the 0.00% is correct:  less
that one in ten thousand.
Oh, I'll risk three decimal points:  one in one hundred thousand.

Very few people get bitten by poisonous snakes in the U.S. every year
under normal conditions (I would assume the same is true in Europe). 
A verly large majority of such bites occur because someone is trying
to kill, capture, or otherwise torment the snake.  Snakes would MUCH
prefer to get out of your way. Also, snakes like to hide in rocks and
piles of wood, not open grass, so as long as you aren't poking around
in these obvious hiding places, you should be fine.

Even when they do bite humans, poisonous snakes tend not to envenomate
such a large foe very seriously if at all, because venom is for
killing/stunning and pre-digesting food.  So called "dry bites" are
not uncommon when poisonous snakes bite humans.  Venom tends to be
biologically costly, so they will use the minimum amount to make their
point (yes, snakes do control the amount of venom they release).

In the extremely unlikely case that you do get bitten, make a good
mental note of the snake's distinguishing features, because antivenin
is semi-dependent on species.  Also, demand (on threat of lawyer if
necessary) that the doctor call in an experienced toxicologist,
because American doctors don't know how to properly treat snake bites
(that's how rare they are!).  You should have plenty of time for this,
especially if you get bitten on the arm or leg; normally at least a
few hours and probably quite a bit longer (Cobras and such can kill
much faster, if your in that part of the world).  If you start dying
too quickly after an American snake bites you, there's a good chance
it's an alergic reaction (anaphylactic shock) rather than the venom
that is killing you, but you probably won't be conscious enough to
point this out to your ignorant doctor.

On the other hand, parts of Asia suffer from tremendous snake bite
casualty rates for various reasons, including the increased prevalence
and potency of venomous snakes, increased contact while working in
rice fields and such, more confrontational attitudes towards snakes,
unavailability of antivenin, and the fact that, if you do piss them
off, Asian species like mambas and cobras are more viscious than most
American snakes like pitvipers .

Irish golfers have no fear of snakes since we don't have any! St.
Patrick is reputed to have expelled them - check this web page to see
how.

http://www.dur.ac.uk/p.j.d.scott/dub/homer.html

Joking aside, if you fear snakes but don't mind a bit of rain and wind
and some fantastic links courses, come to Ireland.

Good luck,

Peter Scott