I've always wondered if you could solve most of the negatives by imposing a "money in per year" limit on online gambling. Let's say, you can only transfer in 1000 dollars per year or something; maybe it's a federal limit tracked to your SSN or required to be declared on your tax forms or something. You can of course transfer OUT as much money as you win, and carry over any earnings to next year without affecting the limit. But aside from people for whom 1000 dollars a year is a huge deal, you avoid the worst harms. The people who benefit the most and eventually become disproportionately represented in the pool are superforcasters who can consistently turn a profit by being smarter and better at predicting stuff than everybody else.