Maybe they can. Wasabi's implementation of coinjoin has reportedly been breached:
Still, it seems that Wasabi has never been as safe as we all think:
Using a capability that is being disclosed here for the first time, Chainalysis de-mixed the Wasabi transactions and tracked their output to four exchanges.
So the guy found a vulnerability in the DAO and reported his findings. But he wasn't taken seriously and the developers thought it couldn't be exploited. To prove them wrong, he hacks the protocol and creates havoc for Ethereum. It really could be that German/Austrian lad. Even so, the article doesn't explain how he did it in a way for a non-computer and tech savvy housewife to use similar methods to discover what her husband has been buying.