The only thing I'm really aware of is the "thundering herd" where you have, for instance, millions of people who have vTXOs who want to get on chain all at once. I think I'm comfortable that it's at least no worse than the status quo where we can't even attempt to serve that many people, but maybe it ends up turning into a "trap" that reks a bunch of people?
Discussion
Haven't heard about this but how would that be any different from millions of people trying to use the base chain all at once? Cuz that would obviously take a good while to process.
It's basically the same, except imagine the difference for users between "I couldn't buy in to Bitcoin because it was congested" and "I bought into Bitcoin but now it's completely stuck because it's congested".
Plus, with L2s like lightning, you need to be able to get your "corrective" transaction on chain within a certain time period, otherwise your channel partner could steal. (You need to get your Penalty transaction in ln-penalty, or update transaction in ln-symmetry confirmed)
I'm pretty sure at least *specifically* with channel factories and timeout trees + lightning, it's not much of a concern, since your channel partner's attempted theft would mean unrolling part of the tree anyway, they actually shoulder most of the fee burden in that scenario, so they have incentive to continue behaving. (Don't take my word on this, I've only half thought it through)
There might be other constructions that create a greater risk though.