Tom, but I just proved that acs_object.name doesn't scale!
As to changing data: if you expect heavy updating/deleting/inserting then you can mumble around with PCTFREE and PCTUSED. Given that the name field is usually quite small there should row migration should almost never happen.
Updating/inserting/deleting into a second table certainly cost, but accesses happen far more frequently.
Following up Branimir's comment: I always found that we had way too many useless joins between acs_objects and acs_objects_description. And I don't mind NULLed columns, they don't take space and don't cost when being accessed.
So here's a step-by-step approach: introduce acs_objects_description with above mentioned fields and deprecate the name and get_url function. If things work out well, then go one step further and try to deprecate acs_objects_description or at least move around some fields (modifying_ip in acs_objects for example looks really useless).