1936
As if it wasn't bad enough that they want me to use a random internet service to add a keyboard to a usb wifi receiver, they have the balls to put this for Firefox users. I clicked out of pure curiosity, as I'm not even remotely interested in involving a corporate internet service in getting my keyboard connected to my computer. This is the message you get now on Logi Options software if you have a Unifying Receiver: 
For the curious: https://logiwebconnect.com
EDIT: some people on the thread have brought up that the error message being displayed for Firefox users is due to the WebUSB API not being implemented by Firefox due to security concerns. This still does not justify having to use a web app to plug peripherals to a PC.
It's fantastic, I can't install the logitech software at work so I've used a Linux laptop with Solaar to add/remove devices on my receivers.
Funnily enough, this web based thing actually means l can now do this on my work laptop..
That's almost certainly why it's a thing. So many people have multiple dongles because they either can't pair multiple devices to one receiver or they don't know that they can
One thing I like about Logitech mice, and I know some other mice have this, but onboard memory to store a few profiles. My work laptop doesn't allow me to install any software so I configure my Logitech G604 on my personal PC, save the profile to onboard memory, then connect to my work laptop.