My Australian friend wants to buy my ticket so I can visit him in Australia, I live in the United States. Does he have to have my passport information and my visa information to purchase a airline ticket for me?
It very much depends on the airline / booking site / travel agent he uses. Some let you enter your passport details when you arrive at the airport, others require it up front (especially travel agents).
Frankly your best bet is to just scan it all and email it to him, then IF he does need it - problem solved :)