One advantage of gibberish passwords like "b923F$5mvA" is that if someone looks at your fingers while typing them, he'll have a hard time figuring them out from

One advantage of gibberish passwords like "b923F$5mvA" is that if someone looks at your fingers while typing them, he'll have a hard time figuring them out from your keypresses, whereas if you typed "this is fun", it would be much easier. Ditto for when someone has a visual glimpse of your password which is only a few seconds long. (e.g. someone looked at your laptop screen while you got an email with your password from an irresponsible website.)