This creates an interesting legal problem, because players may buy additional chips with their credit cards. If players cannot win money or merchandise, the activity is an amusement game. But no state is going to go after an Internet operator for running an amusement game, where the only thing a player can win is the right to play the same game again. If an activity offers valuable prizes and requires consideration, but the outcome is not determined by chance, it is a game of skill and not gambling. For the Internet, the easiest way to run a skill game is to have a tournament, where chance equalizes out over time.
Players play only against other players, never the house, with a guaranteed prize to the winner.
Interesting and fun skill games are difficult to design, especially when players cannot be penalized simply because they have slow modems. Even if there is consideration, prize and chance, the game might not be illegal. Many forms of gambling are legal, and the law can be quite complicated. For example, an Indian tribe in a state where the state lottery has run telephone games probably has the right to sell lottery tickets over the Internet, at least to customers within that state. The only way to know for sure whether an on-line game violates current law is to have a judge decide.