[jerguismi]

Small amounts are somewhat easy to exchange, if you want to exchange millions it gets much, much more difficult since you have to explain the source of funds to the exchanges and banks involved. If you have hacked them they will use blockchain analysis etc.

[diffset]

they will use blockchain analysis

Tumbling the coins would help with this, right?

[swinglock]

If you have to explain where it's from it may be more suspicious if it looks like you took steps to hide the origin, calling for even more detailed proofs.

[aeternus]

Does any currently operating exchange actually care about the origin of coins?

[ar4s]

Most of them [exchanges]]will have tagged stolen coins from known hacks so when they are deposited the account is flagged/locked.

Tumblers/mixers are the most likely place to pick these up.