It most definately should be available to all through matchmaking. Dissapointed to see it not included as I wont play the campaign now as much as it deserves & I would like to. To continuously spam friends is not really an option also messaging, waiting for replies arranging & organising sessions is a bore & a pain, I want to able to just search for a game & play just as in Reach. Please, please, please, 343 add this to a playlist in the near future I beg of you. There were always a few hundred people playing co-op campaign on Reach & even after I beat Reach on Leg I still played co-op to help randoms out & it was fun, the amount of easter eggs & funny stuff I was shown by fellow random gamers (which I could then show to others) was unbelievable & this would not have happened if there was not matchmaking co-op & I would have missed out on so much good stuff, it was exactly the same with Gears3 & it worked a treat. Its a shame for us all to be missing out on these priceless campaign moments due to no matchmaking. Please hear me 343!!
Ps Loving the game though.