Trading cards/betting money and/or cards is the worst idea ever. You could create multiple accounts and fill your deck up with tons of money and cards, for free.
The impossible badge IS possible. I've earned it. Its rather difficult, which is why its an "Impossible" badge as opposed to "easy." It takes a lot of skill, luck, and the perfect stat/skill build to achieve, but the reward is a hefty 60 points. So, just saying, it IS possible.
Too many programming bugs and such. I was forced to overwrite my data due to the game not allowing me to move or shoot after I gained the Third Heartstone Piece. The concept of this game is great, but it still has bugs that need to be ironed out, and small details that need to be added (eg. fixing circle buildings so that arrows/magic bolts don't treat them as square buildings)
 "A Knight's Story 2"){kind=icon}
 "Idle."){kind=icon}
 "Elements"){kind=icon}
 "Heroes of Gaia"){kind=icon}
 "Sonny 2"){kind=icon}
 "Moonrocks"){kind=icon}
 "Hands of War"){kind=icon}
 "Kongregate Chat"){kind=icon}
 "Stippler Jiggler"){kind=icon}