Not so much the potential for money laundering, as actual money laundering. Is there actual money laundering going on in Steam's item marketplace?

Yes, at least back in 2019, from the link:

> However, worldwide fraud networks have recently shifted to using CS:GO keys to liquidate their gains. At this point, nearly all key purchases that end up being traded or sold on the marketplace are believed to be fraud-sourced. As a result we have decided that newly purchased keys will not be tradeable or marketable.

Many users still suspect it happens, although it's hard to prove.