This is the strongest point that comes to my mind. I feel that most consumers are completely unaware that their perception of transfer speeds and file size differ by almost an order of magnitude. I absolutely hate how marketing takes advantage of this. Imagine the frustration after thinking that your 10 Mbit/s connection can download a 6 GB game in just ten minutes.

Many internet operators advertise speeds as "1Gb/s" or even "100M". Add in the confusion between 5G and 5 Ghz WiFi.

Considering ACKs traffic when doing back of the envelope estimates I divide by 10: 100 Mb/s = 10 MB/s (on Ethernet, Wi-Fi who knows.) But that introduces a new problem: how many developers have an idea of how networking works? A smart developer I worked with once told me that he only knows how to turn Wi-Fi on and off.