My bikes are all free for the asking, once the thief makes it clear he (or she?) is willing to use force. My life is definitely more important to me than any one of my 10 bikes, even my $4000 BMC. I will even offer to turn my head as they ride away, so as not to be able to identify them in court.
Of course i have had many people ask me nicely, "Can I ride your bike? Pleeese? I'll bring it right ba-aack . . ."
These individuals are promptly and swiftly advised to go f*** themselves.