user26859: We know that 2 is insufficient and 10,000 is more than enough.  
We also know JoinMarket can achieve about 2-6, Monero 2-3, but there all transactions are mixed, so they add up, CoinJoin can do 400-ish, but 50-100-ish is more realistic.    
What kind of practical or theoretical approaches there are those can help decide what anonymity set should a developer/researcher aim for?

user121984: This is a fun question. I think to answer it one would need to first consider the effort required to identify each member of the set and work backwards from there.
To do that, I figure you might need to specify what kind of threat the anonymity set is facing.
For example:
"What is a sufficient anonymity set to conduct a private transaction"

with a merchant hoping to determine my spending habits
in such a way that a counterparty cannot determine the source of funds in civil proceedings
to ensure that a national tax authority cannot make a reasoned judgement as to the source of funds
to ensure that a complex nation state with virtually unlimited resources cannot unmask the identity of a dissident


26859: <p>We know that 2 is insufficient and 10,000 is more than enough.  </p>

<p>We also know JoinMarket can achieve about 2-6, Monero 2-3, but there all transactions are mixed, so they add up, CoinJoin can do 400-ish, but 50-100-ish is more realistic.    </p>

<p>What kind of practical or theoretical approaches there are those can help decide what anonymity set should a developer/researcher aim for?</p>
 121984: <p>This is a fun question. I think to answer it one would need to first consider the effort required to identify each member of the set and work backwards from there.</p>
<p>To do that, I figure you might need to specify what kind of threat the anonymity set is facing.</p>
<p>For example:
<em>&quot;What is a sufficient anonymity set to conduct a private transaction&quot;</em></p>
<ul>
<li>with a merchant hoping to determine my spending habits</li>
<li>in such a way that a counterparty cannot determine the source of funds in civil proceedings</li>
<li>to ensure that a national tax authority cannot make a reasoned judgement as to the source of funds</li>
<li>to ensure that a complex nation state with virtually unlimited resources cannot unmask the identity of a dissident</li>
</ul>
