Thieves only steal certain kinds of bikes.
Gixxers, CBRs, ZX-10Rs, ZX-6Rs, R1s, R6s, etc...you know, the sport bikes.
Other kinds of bikes get left alone.
Take a Honda Magna, for example. Not one single Honda Magna was reported stolen in 1998, 1999, 2001, 2002, 2004, 2006, or 2007.
In fact, this is a true story: I woke up one morning and found a Honda Magna parked on my front porch with a note that read, "I found this outside last night. I didn't know who it belonged to, but it was kinda in my yard out near my mailbox. I thought it might be yours, so I washed and waxed it for you. Have a good day."
See? Get yourself a Honda Magna and sleep EASY tonight. Hell, park it with the keys in it and running. It'll be there in the morning--you can count on that!
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One's chance of survival is inversely proportional to the magnitude of one's ego.