According to a study released by Nucleus Research and KnowledgeStorm, 1 in 3 users write their passwords down.
This of course opens a method to have that password disclosed accidentally. Give your uses some good tips on how to create good passwords that they can remember, and not need to write down!
Now why the yellow Post-it Note? Well, what is convenient, small, and easily posted somewhere? You guessed it. Guess what is also the first thing I look for on a dumpster diving expedition? Post-it Note Gold!