6) Well, from a usability standpoint, I think that the best answer is A > B > D > C. Why?
Really, liquidity mining is stupid. It's similar to transmining, creating effectively negative fees to create the impression of activity. People should use a product if it's useful!
True, but the scale here matters. FTX has $1b/day and pays about $750kmonth for liquidity; Balancer has roughly no trade volume and is paying $12m/month for it.
In particular:
if payments are in line with volume and use, they help get more liquidity.
If payments are way greater, they create unused liquidity aimed at the incentives rather than trading.
ok, so you mean decentralized liquidity mining is inefficient
i agree in the cases of comp and bal
but i also think it's worth recognizing how fundamentally different and more difficult it is doing these things in a decentralized way