My 6 year old was riding around the front yard some time back and then went next door to play with the kids there.

She had just left her bike lying on the ground outside so I took it out the back and put it in our shed.

I waited for her to come back home then asked her where her bike was and where she had left it.

She very soon started to think that someone had taken her lovely bike and her eyes welled up with tears. I then told her that her bike was safe but that she had been very foolish to leave it there where it could have been stolen.

She's now very careful with her bike. (To the point where when we cycled to the park the other day she instructed me to watch the bikes while she played on the playground equipment.)

I guess the difference with this kid is that he has already had it proven once that if he gets his ride nicked, his folks will just get another one.