Yes, there is malicious software out there that encrypts files on your computer and directs you to a web page where, for a fee, you can buy the decryption key. Or just restore from a recent backup (you do make backups, right?) But that's not what I'm here to talk about tonight.
Closed-source software vendors are holding their customers to ransom. If you don't buy the latest version of their products, you won't be able to read anyone else's documents if they have upgraded to the latest version. But what is especially galling is where electronically-identical hardware appliances have features enabled or disabled purely by software.