Today many potential new player will want to try the multiplayer mode first, not bothering with the campaign or skirmish.
Let's ignore the problem of not enough people in the lobby for a moment (it's seems to be getting better lately anyway).
However most people will not have their systems set up correctly for multiplayer (firewall, forwarding ports). However people just see an empty lobby, not knowing what the problem is (unless they later read the readme files, FAQ and forums with their contradicting info).
It would be much better, especially for new players, if one would get a descriptive error message in this case: When goes to the lobby and can't connect to the metaserver an error message telling about the problem and which ports to open should appear. Even better would be if there would be some kind of check testing if connections from the outside to the respective ports get through, so people know about the problem of port forwarding (instead of just wondering why no one wants to join their game).
Philipp