i've wantonly done worse with my laptop and cameras than accidentally falling onto them.
i've also learnt that padded sleeves and linings are useless if you forget to clip/zip shut your bag, and that accidental damage insurance is a wonderful thing.
go to a camera shop and get a load of that replacement cubed foam for hard camera cases, and get someone to sew you a bag to fit around it, and put that in your messenger bag. put your laptops or cameras or scotum or whatever in that.
fsnl
sparky