[jveritas]

If I may ask why you write G-d instead of God or GOD? Why you do not fully write the name? Thank you.

[agrace]

Simply out of respect for my Jewish friends. Many see the name as so holy that they don’t write it out, and traditionally what they use is actually just that, HaShem, meaning, the name.

[dervish]

To refrain from taking His name in vain.

http://www.amichai.com/the_ten_commandments/three.html

[Marysecretary]

Jews believe God’s name is so holy that they aren’t supposed to write it out.