People are welcome (and encouraged) to pick stuff up wherever you find it, or at any camp or art installation you frequent, but ultimately the MOOP responsibility lies with the people who brought something to that space (camps, artists, mutant vehicle throwing it down in deep playa, etc).
For the sake of clarification (since the thread's about Opulent Temple, and I'd hate for anyone to confuse them with Rites Of Zion/Temple Of Boom's poor performance in 2011), Opulent Temple did a much better job. Here's a look at the 2012 MOOP Map, OT was located at 10:00 & Esplanade.
Yep, they got some red in there. But I think that's significantly less red than they've ever had, and a pretty small amount considering the size of their space and how many people were in that space every night of the event. When they return at some point I expect they'll continue to improve.