Well if you watch National treasure you will see how easy is to spot the common keys that you press with a special fluorescent/UV light , also the fingerprints on a keyboard are more visible on thouse keys (that would be the keys for sudo for example , or the login window) also some social engineering helps (knowing the person)
- I'm here.
- Give me the letters for her password.
What do you got for me?
Hit me with it.
Anagrams being listed.OK.
Top results: "A glove fry."...
- It's "Valley Forge"."Valley For..."
I don't have that on my computer.It's "Valley Forge" -she pressed the E and L twice.
Valley Forge was a turning pointin the American Revolution.C
an I marry your brain?
That is why is better to use the ssh-agent , password-less sudo
and spread your password keys over your keyboard , and one more hint
it shouldn't be any reference to anything known about you in public/private life (eg if you love history:historical references with years dates , places)