I hope Halo: Reach allows you to search for other people's custom games which have been created in forge. Being able to search for a custom game is a standard thing. I don't understand why Halo Reach shouldn't have it. A host's list like Gears of war (with searching tools) can be great for Forge. If we don't have any way to play with other players in our maps exept our friends list, Forge will not be exploited enough. Why should we create maps if we are alone in our maps ?
Why should I have to make friends with random people on the Internet just so I can play with them more than once? If there was a host's list system I could keep my current friend list while comfortably finding fun maps and game-types people have created without monotonously scrolling through my friends list hoping one of them happens to create a entertaining custom match. It's too irritating, we shouldn't have to guess if there's a fun custom game, we should be able to find custom games right there and now, especially with the idea of Forge world.
You may argue some of the custom games created might not be good. Bungie could use a star rating system which would ensure that the cream always rises to the top. There might be too many servers, Bungie could use a server filter. What I'm trying to say is that for every problem you may point out, there is always a solution. Let's face it, custom matchmaking would make Halo: Reach stupendous and would certainly attract more gamers out there. I still have my fingers crossed that Bungie does something comparable to this.