As for dangers to your hardware, probably not much. I've tried writing a few times to the 2730A as I'm debugging, and the only thing that has happened so far is the radio beeps, displays CLONE ERROR and I have to power cycle it, after which the memory is reset. That is using the wrong protocol, though, and not writing bad data using the right protocol, so I'm not sure what happens there yet. I would imagine it might just display an error or reset itself if there's bad or corrupt data. You are unlikely to be able to actually harm it, but, of course, that's not a guarantee.
Icom radios are very robust against harm from the memory image. All the ones I have experience with validate the image as it's coming over the wire, and as soon as something nonsensical is found, the clone stops, the radio resets itself (like actually) and then reboots.
I've had Yaesus at near brick state as they are not very robust. They also don't generally actually clear the memory when you ask them to, which means cleaning up a mess isn't as easy as a reset.
The chinese radios will take anything you give them, but despite occasionally writing garbage into them while developing, I've never had one of them not come back from the dead (your mileage may vary).
Kenwood radios, when programmed via the live protocol, are also highly resistant to you doing anything wrong.
I totally understand the concern, and it's good that you know it's always a possibility, but in ten years of doing this, I've not generated an three-digit paperweights :)
--Dan