I'm hearing about cases where companies got hit with cryptolocker type viruses. And it wasn't something just just happened in a 30 minute period. It was a sleeper virus that waited 72 hours before activating, which invalidates all of your recent backups. All it would take is a sleeper to take 1 month, 6 months, etc to activate and then bam - you're done. No good backups. No data = no company. It would be a nightmare.