When an investment method is proved to generate profit,
others will follow, and eventually such method will lose
its effectiveness. This is how things work, so
seeking a permanently profitable "investment model"
is completely futile to begin with.

Efficient market will generate, in average, normal
returns appropriate for the system risk one takes, as
the CAMP model would suggest. However, in an imperfect
world such as the one we are in, inefficiencies
exist and constantly being created by novice
"investors". Experienced investors as well as
predators benefit by skimming profit from inefficiencies
created by less informed individuals, picking
money from one pocket to another.

So, Steve is right in that the market is not zero sum.
Long term profits are proportional to system risk
as well as return on capital.

It is not a valid question, however, to ask whether
there is a method exist to generate "abnormal profit"
constantly exceeding that of the market return.