Unlimited ERC20 allowances considered harmful

ERC20 allowances are integral to the functioning of many DeFi applications and other smart contracts. But (too) many dapps use unlimited ERC20 allowances, which exposes users funds to additional bugs. There are several things dapp developers can do to mitigate this, most importantly giving users the choice not to use an unlimited allowance. There are also several things that users can do, most importantly revoking unlimited allowances to dapps they no longer use.