Sorry if I pissed anyone off, it's just I too find this debate (the general, rather than this specific case) very tricky and very interesting but things just seemed to be getting a bit snipey.
For what it's worth (which I know aint much) I do believe this is SO site specific that without a huge amount of information (which I'm not denying anybody here has BTW) it's so tricky to call, and even then its hard.
Take the Seahenge thang, which I think was mentioned earlier, the choice was, effectively a)leave it in situ where it is almost certain to rot away being as it was uncovered by a erosive storm event which changed the character of the area it was situated in; and was therefore unlikley to be recovered any time soon. A course that would make a lot of people who believe that respect for the ritual placement of the thing should outweigh the academic desire to study it or b) Take it away to be preserved and recorded, ensuring its survival but simulataneously desicrating it and making it (until it finally goes on display properly) visible only to an 'archaeological elite'.
Now in the case of Seahenge I tend to side with b although it's a tough call.
Rock art is even trickier, in many cases it has been in the process of being eroded for thousands of years to little detrimental effect so why not leave it? However one could also say, 'well nows the time to finally start looking after this stuff.'
In this particular case, if the fire has indeed caused the carvings to become even more fragile, it opens up an even bigger can of worms.
Point is, I guess, and as a few people have already mentioned, there is no catch-all solution and, pretty often not even a 'right' answer for each specific site.
Sorry again for (I realise) being snipey myself but I got a bit worked up...
