Here's what I have on mine: Documents scanned in.
Info for myself & wife.
Social Security card
photo of self & wife
Birth Certificate
Will
Drivers License
Diplomas High School
Regents
AAS
Baptismal Certificate
Medical History
Medical insurance
Car & truck Registration
Title
Insurance Card
USMC DD 214
Marriage License
House Insurance Info
Pet Information:
Pictures of pets
Merlin License
Immunizations
Freydis Immunizations
Victoria Immunizations

The comment about identity theft is a good one. Hopefully, USB will be around for a while. I think that a USB port is standard on computers now.