It lets people of their own free will exercise their judgement to wager on sporting and other events. Unless you think all gambling is by definition unethical for religious reasons, I'd say they were pretty legit.
Gambling is mathematically negative sum. Its a fucking stupid tax. That is ethically dubious for non-religious reasons.[0]
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Betfair's business is illegal in the United States[1]
Betfair faces millions in fines after content ruled illegal [2]
[0] It is activity tolerated (cynically) for its ability to raise taxes, and even then only in small doses.
But I believe if you do some google research, there are other concerns.[3] These include things like time-delayed feeds to support real time betting (and fraudulent front running) as well as a variety of your typical deceptive TOS pseudo-scams (bonus schemes, etc).
