Well, with HBD I think the main concern is that the witnesses don't keep the protocol debt in check and limited, if they don't, they could cause an implosion of both HBD and HIVE.
They've been doing a good job so far, especially when compared with a protocol like Steem which has a bunch of SBD vs Steem which might very well cause it to implode in the future.
@edicted knows more about the protocol debt metrics then I do and I know he made some good posts about it in the past which you should ready if you haven't.
He is probably one of the best people to follow and ask about the stability of HBD and HBD savings rate.
I never liked AnchorProtocol, smelled like bad ponzinomics ready to blow, which it did...
ThorSwap loans have similar mechanism, but at least the people "in charge" have limited it and know of the risks.
With Erik Vorhees from shapeshifting telling me himself that it is limited, which I can assume means they understand the risk:
Great insights on Throswap. I have followed Erik from his centralized days. Never looked into Thorswap loan though. I find it a bit complex to navigate. I have a Rune-BTC pair experiment that I am holding since the last bull market.
With HBD, I do not have enough $$ to too much worry about the situation. I have read @edicted's posts but I do not fully understand the risk of the loan system yet. I am giving extra benefit of doubt to HBD just because I spend my time here in the ecosystem. But f Ups are f Ups and can happen anywhere.