I'm not an expert at SNMP, but isnt an OID (Object IDentifier) just an entry in a database?

What i mean by this, is an OID is just a reference point, to get the associated information from - (or am i incorrect). The point being that i would expect an OID is get and walk-able by the very nature of what it is, meaning if you cant get it, you shouldnt be able to walk it either.

I would also think that a walk is a recursive get.

Again, I have to disclaim my knowledge of SNMP is quite limited.