Where or how did the tradition originate on blowing out candles on a
birthday cake?  Not exactly sanitary!

Material here may be of interest to you:

http://teacherlink.ed.usu.edu/tlresources/units/Byrnes-celebrations/bday.html

http://www.everything2.com/index.pl?node_id=953824

I don't know where it came from but it certainly beats other
traditions. In the Bible, on "his" birthday, Pharaoh celebrated by
killing the baker:

"Gen 40:20  And it came to pass the third day, which was Pharaoh's
birthday, that he made a feast unto all his servants: and he lifted up
the head of the chief butler and of the chief baker among his
servants."
Gen 40:21  And he restored the chief cupbearer back into his cupbearer
office again. And he gave the cup into Pharaoh's hand.
Gen 40:22  But he hanged the chief baker..." 

tutuzdad-ga

Hey, that is one biblical passage that I never read!

So it is all about "Pneumancy" from one of Pink's links:

"divination by blowing, of candles, etc. [Gk ?v?v?? (pneuma) wind]
1955 Shipley Dict. Early Eng. (1963) 17. pneumancy, blowing; a
vestigium of this is the blowing out of candles on a festival cake.
NOTES: not in OED"
http://www.webspinning.com.au/home/lambertj/public_html/p.man.html

Tutuz, the killing of bakers wasn't a birthday tradition in ancient Egypt.

According to biblical commentaries, the baker and the cupbearer (aka,
butler) both "offended" Pharaoh in that a baked product had dust (or
similar foreign matter) in it and a cup of wine had a bug in it.

The two were tossed into jail with Joseph, who interpreted their
dreams and predicted the baker's death and the butler's return to his
position. After this comes true, the butler later recommends Joseph to
Pharaoh to interpret a dream. The baker remembered nothing...

Thinking about the responsibilities of the men leads to the same
logical conclusion Joseph reached-- the cupbearer, despite diligent
service, could not prevent a fly from plopping into Pharaoh's cup a
moment before he drinks; but the baker very obviously was lax in his
duties to allow foreign matter to contaminate the baking product(s)
and not be noticed either during ingredient preparation, mixing,
kneading, pouring, forming, post-baking, and preparation for delivery.

Smart cookie (heh heh), that Pharaoh. Impressive management skills and
a keen insight into employee behaviour. Especially as regards
motivation.

Yes, I know. It was apparently a failed attempt at humor.

tutuzdad-ga