Everyone know someone that's fallen off a ladder. Falls are the #1 cause of DIY Fatality
Interestingly, electrocution ranks #3 - Always use a licensed tradesman when dealing with electricity.
References
Unintentional (Accidental) Hospital-Treated Injury (Victoria, 2011)
Do-It-Yourself Jobs: Information for the Home Handyman
Do-It-Yourself Jobs: Information for Workplace Managers
2012 National DIY Safety Report by 3M Tekk Protection