Two kids are riding a bike. One of them is balanced on the handlebars. They go down a steep dirt driveway--it's bumpy, too fast--so, the kid on the bars jumps off but is now in front of the bike. The kid in the saddle applies the brakes as best as can be, but the nutted axles dig into ankles of the kid that is trying to outrun the bike. Lawsuit? Should have been acorn nuts? Should have had plastic covers on the axle? Should have had QRs? Should have had a warning sticker on the bars or bumps that make it uncomfortable to sit on them? If the bike comes with nuts on the axles, do you have to provide a wrench; otherwise, are you liable if the rider is stranded in a bad part of town because he cannot change out a bad tube?