I happen to agree with PG that Poker is a growing problem. But to say that Poker is not gambling is ridiculous. If you are playing poker you are gambling money to try and get more - just like the stockmarket is a gamble too. It doesn't matter whether you loser your money to another person, the house or the market - you still lost you money.
Here is the Dictionary.com definition:
gam·ble
v. gam·bled, gam·bling, gam·bles
v. intr.
To bet on an uncertain outcome, as of a contest.
To play a game of chance for stakes.
To take a risk in the hope of gaining an advantage or a benefit.
To engage in reckless or hazardous behavior: You are gambling with your health by continuing to smoke.
v. tr.
To put up as a stake in gambling; wager.
To expose to hazard; risk: gambled their lives in a dangerous rescue mission.
n.
A bet, wager, or other gambling venture.
An act or undertaking of uncertain outcome; a risk: I took a gamble that stock prices would rise.