Backpacs?

[fazersharp]

Because they are attached to your bike instead of your back?

I witnessed it in my youth when a mate came off his moped on the way out of college. As he came off the bag caught on part of a speed bump and stopped his dead (from around 20mph) the force from the straps snapped his collarbone and the bruising/welts were insane

I know that he was probably just unlucky that it caught but I prefer not to take the risk.

I see
So why haven't they come up with straps strong enough to hold but yet snappable in the event of a snag - cannot be that hard.