You people are spreading misinformation, ice CAN cause an infection, if your lungs build up too much moisture inside of the air sacs (when you breathe in with ice in the chamber you breathe water vapor) you can contract infections or pneumonia. You just need alot of it, thats probably why your friend got the infection because he was smoking wiht ice a heinous amount of times, that can wreak havoc on your lungs.
Which basically means that most casual users of ice will not contract infections, but it is certainly possible with prolonged use.
EDIT: I am not a doctor, this is just from things that i have read in the past.