Rookie Hails Fellow Rider and Crashes Silly [Video]
Now, hailing other motorcyclists a guy encounters during a ride is indeed a polite and a brotherly thing to do, but there's no hailing techniques manual. Some people nod, some flash their lights, while others use their hands or just beep their horns (when passing others or passing by stopped fellows).
Not hailing incoming riders may be looked at as impolite (worse then my laughing), but in case of people who are not sure on their one-handed bike steering, keeping both hands on the bar is probably preferable.
Adding a turned head and no awareness for what's happening in front of the bike only makes things worse and will lead to a silly crash.