It's massively common. USDT is the usual coin of choice because even though the ledger is public, the convenience and relative stability massively outweighs the security risks. In the jobs I've seen, the marks will be 'investing' in BTC but the criminals will be moving those funds out into USDT the moment it hits the bandit wallet.
USDT can be frozen so its not the best choice. Its definitely a failure of the Tether team if criminals can openly use it to launder funds without it getting frozen, but they are famously anti regulation.
The usefulness in money laundering is a feature not a bug, and is why Tether is permitted to continue operating.
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From what I've heard about Tether (allegedly printing tethers backed by loans to insiders, or backed by very risky commercial paper, or even potentially billions of USDT backed by nothing), I think being useful for money laundering is the least of anyone's worries...
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