The ultimate risk of losing data is the accidental deletion of our files without any backup. This is the most common cause happened almost every day. Not a surprise if we accidentally delete some files or overwrite the parts we did not intend. Many people failed to perceive the risk ahead.
Another thing is viruses and malware. There are tons of malicious software which attack computers every day. Being connected to the internet also entails risk and can result to tremendous data loss.