Dusty Schmidt's article in the latest issue of CardPlayer (December 21, 2010) magazine is titled "A Game of Skill, and Therefore a Job--Why playing poker qualifies as a profession". While he doesn't mention the word "gambling", what he has to say below is certainly germane to answering the OP question. I've inserted that word where I feel it pertains to the issue.
To me, defining poker as a game of skill is actually quite simple. To do so, you just need to forget about winning at poker and think for a moment about losing. Is it possible to intentionally lose a poker game? Yes, of course. But is it possible to intentionally lose a game like roulette or craps? No, it's not.
In games of chance [gambling], the participant cannot control the outcome. Whether your intent is to win or lose the lottery, your odds remain the same. The superstitious may disagree, but no matter how many times you pull the handle of a slot machine, your odds remain the same each time you put your coins into the slot.
But in poker, your actions can influence the outcome of a hand. You will absolutely lose if you fold to every hand no matter what cards you hold. If you call bets with a hand that cannot win the pot, you will also lose every time. This is the difference between a game of chance [gambling] and a game of skill.
It's common knowledge among poker players that chance is a factor in any given hand, but over many hands, poker will even things out, with the more expert players making a profit.
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