Oh this kinda stuff still works. You can even send emails and as long as you got html email, they are too stupid to know where it came from, rofl. Oh and the harvad youtube video? To answer the question why some people notice and others don't? 2 variables, 1 the person is thinking about something else, or 2 the person doesn't perceive or see the material as it doesn't exist. What about the hidden messages in Lady Gaga's songs; most people are too stupid to know what they are, just like Justin Bieber, as those songs ain't written by them and they go through a panel of experts, who after purchasing the song can do whatever they want. The lyrics are one thing, but if you listen to trance music for example, so many layers and sounds exists, melodies, often I don't even hear a sound in a song until the 50th + time hearing it.
It's the little things people never notice, sometimes obvious, sometimes hidden, that are the keys to corporate deception. The best spamers and fishers use these psychological methods of manipulation, just as the best marketers do. Psycho analysis is a very good topic to research in your spare time.