Several ancient petroglyphs were sawn out of the Sierra cliffs in SoCal, while a number of others were defaced as a result of apparent attempts at removal. Although sacred to the Paiutes and Shoshone Indians, the site was managed by the federal BLM (can't wait for the feds to start managing our health care).
BLM immediately implemented their first line of defense in an effort to ward off criticism: they don't have any money, so they can't police the area. Really? They can't mount a few strategically-located cameras with radio uplinks? That's cheap technology, these days; certainly less expensive than, say, fencing access points to the area and closing public access - which is another option.
Basically, BLM screwed up from the get-go, which may be hard to imagine being that they're a federal agency and all, but there it is. Anyone with half a brain would have taken photographs of the glyphs, making them available for public viewing while keeping the specific locations under wraps. On the other hand, there's a reason why they work for the government.