I didn't know it was a problem mine hangs on the front brake lever along with my gloves and glasses:ap:57:
If I feel it's safe, I'll just fasten the chin strap and hang it on the handlebar. If I want to lock it, I've got a cable-style gun lock that fits through the D-ring that I can use to lock it onto the bike. The lock seems like cheap insurance; many gun shops and police departments will give them away or only charge a couple dollars for them.
Of course the real question is, "How do you know that you got where you're going?"