It's complicated, and I'm not sold on the Lightning Network as the future, but
> Which can be be reneged on if one party is malicious, meaning they'll only occur between trusted parties?
This is not correct. My understanding is essentially each party is tying up Bitcoin as being between them on the blockchain, then trading cryptographically verifiable assertions of each other off-chain about what the latest status of the ongoing "tab" is between them. Either of them can close the tab at any time and reconcile to the blockchain.
They don't really need to trust each other, although this does introduce a dependency on some entity (whether the user's own server or a third party) to publish the latest version of the "tab" if the other guy maliciously tries to publish an older version of the "tab." And of course, that means you need some redundant storage / handling of those cryptographic assertions from the other guy about what the status of the latest "tab" is. But that doesn't require trust--you'd want to do it even if you trust the other party.
Or at least that's my understanding of it. I like the conceptual idea of LN but some of these details seem like dealbreakers to me.