Independent Ethereum educator, angel investor and advisor. 

Founder of /thedailygwei.

Heard @sassal.eth (whom I'm a fan of) say that DA layers will become a commodity and their only differentiator would be economic security. Wouldn't decentralization, privacy/censorship resistance, light node compatibility, etc be differentiators among the design options? Does anyone have more insight into his argument?

I don't think I said the only differentiator would be economic security - I believe I also said the same things you said would be important too!

Mainly comes from the fact that the main reason L2's want to use off-chain DA is because its cheaper than L1 so in that world, the cheapest DA wins.

Then, once all DA is costs the ~same, the DA layer needs to offer something else to entice the L2's to stay (that something else is what we discussed above).

Oh, sorry. I misunderstood you then :)

But where does the "commodity" argument come from, then? Or would it be considered a commodity in the same way that processing power is, with the only differences being similar to those mentioned in my original post (which makes Ethereum goat)?

P.S.: Farcaster is awesome.