There are certainly handoff errors, but the vast majority of these can be avoided with a well structured handoff with safety-checks built in. The problems that make handoff bad include:

1) Handoff being done at the end of a long shift, so the doctors handing off their patients are tired, sick of working, and desperate to go home

2) Handoffs being interrupted by sick patients (understandably so) - I was once in a handoff that was abandoned half way through because of a cardiac arrest that half the team had to run off to

3) Rubbish handover systems - most hospitals use hand written notes on scraps of paper carried round by doctors; these can be lost, misread, or accidentally forgotten. There are some technological solutions being developed, but few hospitals have employed them so far