It kinda depends on what's being done. There are a lot of physical systems that are capable of damaging themselves if they operate in an unconstrained manner -

It kinda depends on what's being done. There are a lot of physical systems that are capable of damaging themselves if they operate in an unconstrained manner - so the limitations are software defined. Look, for example, at what Stuxnet is capable of doing to industrial centrifuges. Now, it's somewhat unlikely that user defined software will cause damage comparable to active malware - but mistakes do happen. (marcus0x62's comment pretty much invalidates what I just said.)