We have the ability to mute the text of any spamming object, but not the appearances.
When visiting the public grounds of any default home location in SL, theres lots of avatars, many of whom I find spawning grey-goo style attacks. In one instance I recall seeing a shower of concrete hunks atop many avatars, and these trapped the poor new signups underneath the rubble.
Now, under the current paradigm, one simply abuse-reports and teleports away, walking on top of the unsightly rubble until someone comes and cleans up the rogue prims (or they llDie). What if we had a feature that would allow a given avatar to "mute" a collection of prims, or all prims created by a single avatar. The muting effect would effectively remove the visual and physical influence of the object from the environment as a whole.
Visually, I can see it easy to produce, just filter the relevant vertex information updates client-side, and suddenly you can see through that annoying texture!
The REAL issue however is somehow ignoring the physics interactions. It's trivial to make some undesired objects phantom if all avatars in the sim have them set to "ignore", however if there is a limited subset of avatars that are not ignoring the set of unwanted objects, the physics engine then needs to follow two different trajectories in "causality space" to produce an accurate simulation.
This scales quite terribly, as the programmers here may imagine, for now you need to compute each interaction based on the number of ignore parameters specified by many avatars and possible non-overlapping sets of undesirable objects.
Of course, certain tradeoffs can be made. A landowner could wish that no prims spawned by other avatars have any physical interaction with his sim that would modify the arrangement of his stuff. Now you only do momentum conservation for a smaller set of objects, but then there is the issue of interaction of objects between two non-landowner avatars.
I certainly do not see the solution in sight, but taking the comparison to older web technologies:
One can trivially ignore all users on a particular web forum or within a chatroom, yet the conversation still flows in a single direction because everyone else may still be listening to the remarks by the ignored individual. Extend this to 3d, and this would imply that an ignored avatars bullets do not affect you (you do not even see them), but another avatar falling after being hit by a bullet will drag you down as well if you are in his way.
So, if SL were to evolve into a staple of internet infrastructure, how could one possibly design a sim with the shear traffic volume of, say, slashdot, but also allow every avatar to comfortably fit within the same 3d space and interact with one another?
Lofty, perhaps metaphysical discussion, anyone?