That sounds like a highly specific confirmation that I seem to have missed. Any idea where you might've heard it?

"As you enter certain areas of the game, the server will register which of these are public domains/combat areas. If you stumble into one, it'll automatically, and invisibly, search for another gamer to matchmake you with." -Kotaku I combined that quote with another one that stated you don't have to fight people if you don't want to. I either missed that quote in the article, or it's in a different one. But if you really need it, I'll try to dig that one up too.

I remember this too but unfortunately not where, Kotaku and IGN seem the most likely places.

Well there was talk about being able to play the game solo if you wanted (virtually solo, anyway), but even if that was confirmed, "interactions" could just be trading items or something.

Found it [quote]“Everything that’s fun to do is more fun to do with your friends,” Jones mused. Naturally, of course, there will also be a fully featured competitive multiplayer mode, though neither Jones nor anyone else from Bungie was willing to offer even a hint about any details just yet. Well, other than [b]the fact that you won’t be forced to engage in player-vs.-player combat unless you explicitly desire to.[/b][/quote] This is what we were talking about, I think it implies that there will be some sort of in-game PvP, maybe akin to Borderlands duels. This is of course in addition to regular MP.