I think there well always be inconsiderate people screwing jumps up.
The "no dig no jump rule" is a tuff one, because some people don't even know how to use a shovel, i have had to demonstrate tool use to many riders and half the time it just does'nt sink in. Although any help is better than none.
If it's a kinda secret spot you usually only get riders there that willing to help, and if they don't, there is in most cases a local there that can enforce the rule.
Places like red hill (syd) have riders passing through all the time, they stop for a few jumps and leave, as long as they don't stuff any jumps up, i think its fine. If they start coming more reguraly, they need to put in some type of effort to help. Most jump builders appreciate help even if you only help for half an hour.
There definetly needs to be some kind of rules that people follow, otherwise localism as you see at surf spot well become rife, i personally know what this is like surfing at Maroubra for 12yrs. We don't need that type of neanderthal mentality coming to MTBing.
If the greater MTB community does'nt start working as one, it is going to turn more ugly than it already has been with trail closures, jumps bulldozed left, right and centre and riders getting pumped for not fixing the jump they just cased. I for one don't want this to happen and i'm sure most other riders don't either.