Cool Prof. Snow here!
People can be pretty crafty when they try to find ways to obtain more cards, this can include trying to get them from your account O_O!
So no matter how much "free" stuff someone may promise you, NEVER give out your account password to anyone. Mods and even the support team will never ask for your password, so no one else should ever be asking for it for any reason, and definitely don't enter it into any suspicious websites :S
Make sure to take the proper precautions to protect your account. Remember that you are the first line of defense in preventing Team Rocket from taking all of the Pokemon!
This has been a public service announcement, because knowing is half the battle.