ICYMI: Prelude to my #TLC2019 talk was two cautions: 1. Fees will rise on LN. 2. Long-held HTLCs will be penalized. Let me tweetstorm that at you now...
LND's default fees are 1 sat + 1ppm. The proportional part can only go down to 0; we're already seeing that raised by nodes, and there's clearly room for this to grow. 100ppm == 1 basis point, so we're 100x smaller than the fin community can measure!
Also, fees in lightning are currently pay-after-success. But some kinds of spam are best dealt with using a pre-pay system. To be incentive compatible, the pre-pay needs to be << than the success fee, implying that success fee needs to rise, to avoid Death By Spam.
Similarly, long-held HTLCs (sometimes called "hold invoices") can be done today with LND and c-lightning. But they're also trivial to weaponize, so the network will have to eventually have a timeout which forces channel closures on perpetrators (details omitted for brevity).
This means: don't build a business model on holding HTLCs for minutes, or hours. That will eventually fail. Sure, do that today, but have a plan B when it gets classified as abuse.
Because if we *don't* address abuse, nodes will start de-anonymizing traffic so they can do it themselves. It's that or cease functioning as they get buried in spam attacks. And lightning without privacy is dead; just use a damn credit card.
