Market conditions change, and many things could threaten your ability to turn $1 into $2 -- adwords prices changing, competitors, macro-economic effects, etc.

Market conditions change, and many things could threaten your ability to turn $1 into $2 -- adwords prices changing, competitors, macro-economic effects, etc. Further, the more capital you have, the larger your bounty. In card games or board games, you've created your "engine" -- that isn't victory, but it is a necessary step toward achieving victory.