Matchmaking ruins communities, turns the game into a more solo affair, seen it in many other online games that have added it in. The more effort you put into finding a group yourself, the more you'll get out of it. If the group you've found is good, chances are you'll all add each other and play together on more than one occasion. This is what Bungie are trying to achieve, they're promoting teamwork and tactics, tight knit groups, lasting bonds with other players etc. That's something you're not going to get with matchmade activities, look at the weekly strikes for example, extremely rare that anyone ever talks while doing those in matchmaking, in turn leads to you never playing with that person again. That said, I can see matchmaking working on a basic level, for example adding an easy mode to raids and having them matchmade, it would serve as a nice introduction to raiding much in the same way PoE does with its easy mode. I can't see this working with the harder difficulties though, it will just promote more bitching and whining in these forums (there is already enough of that) about how hard the game is or why xx player is away for the entire time.