I think there are a lot more reasons why paraliminals will not work for all people.
Your learning style would be a big factor: some do not respond well to verbal instructions, doing better with visual stimulus for example.
There's also left and right brain dominance to consider. Paul Scheele carefuly designs his Paraliminals to talk to your left and right hemispheres in a certain way: a logical, rational monologue for your left side and an artistic, non-linear monologue for your right side. Not everyone is wired that way; left handed people for instance.
One more factor that I've recently become aware of is your mother tongue or the language you spoke when you grew up. Beleive it or not your subconcious can respond quite dramaticaly to a dual-induction tape in your native language while having giving you marginal results on an english tape/CD.
Cheers!
