: 50-60% online population were in MM
: 40-50% online population doing other stuff like multiplayer customs, campaign
: single player and co-op, theatre, forge.

: It wouldn't be wise to underestimate Customs population and really, if
: dedicated works for MM, it would work just as well for customs.

In other words, Matchmaking had 10% more people than every other mode in Reach combined. Yes, that's big.

But it's not just a question of numbers. It's a question of how much benefit is gained from spending resources on dedicated servers for each mode. In the case of campaign, theater, and forge, very little. In the case of custom games it varies (i.e. a dedicated server provides much more utility for a pro 4v4 scrimmage than General Vagueness shooting needles into a wall), but on balance it's not likely to be greater than the benefit to matchmaking.