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.