In sports betting contexts, you're often just betting against other players, I believe. If they're anything like prediction markets, the exchange isn't going to care how successful you are, as long as you're betting.

They're not like prediction markets. They do exactly what GP says they do: if you win, you effectively get banned (max bet sizes shrunk toward $0). If you suck, they do the reverse and expand your max bet sizes and offer you loans.

These things are so unfathomably antisocial that I earnestly believe every single politician who advances them should be (journalistically) investigated as extensively as is legally possible.

There are lots of places where you can bet against other players now. The older betting markets like Betfair are no longer available in the US, but Kalshi, Polymarket, and others now offer the same kind of two-sided marketplace in the US.

There is parimutuel betting, but the payouts change based on the final pool size

Not only do winning players get quickly banned like sibling said, the house take on the major platforms is vastly higher than with traditional sports betting.

>the house take on the major platforms is vastly higher than with traditional sports betting

What kind of markets is this referring to?

Polymarket still charges 0 fees. While Kalshi's fees+spread can approach or even exceed traditional sportsbooks on some markets, neither of them have any interest in banning winning players, as they don't take a side on any bet and directly benefit from more betting activity. Kalshi also pays interest on bets, which can add up on longer term positions.

Betfair has operated with a similar model for decades in the UK and elsewhere.

I was referring to platforms like DraftKings, which are extremely sleazy. I think Polymarket and similar low/no fee markets on the other hand are awesome.