An update from the Daily Beast…
NY Couple Not Terrorists, Say Cops, Just Rich Kids With Drug Habits

But further investigation produced no indication that this was a case of Gossip Girl gone terrorist.

“So far, no plot,” the senior police official said.

The official did not offer an explanation as to why the couple had allegedly amassed all the requirements of a terror cell but apparently not the intent. The absence of drugs in the apartment has apparently not dissuaded them from taking the view that the two are junkies with advantages.
…..
People with extensive knowledge of the Occupy Wall Street movement were saying that they had never heard of Greene. They discounted a news report that he was an OWS activist.

By midday Sunday, police had reached the tentative conclusion that the explosives and weapons were part of some drug-fueled fantasy life. To cops, Greene appears to be living proof that going to Harvard does not necessarily make you any less a knucklehead.

As I recall the explosives charges included something like “intent to use” which seems to me like there was some sort of plan to use the explosives for something. Maybe they were going to try to kill some of their rich parents for inheritance money or something. Making the explosives is a lot of effort, i think they had something in mind.