I'd have to say that, while I agree that lobbies are necessary, I also agree on the part that says strictly private rooms might make people miss racing with some of the best out there, and know new people, making it harder to have fresh meat join us.
Best solution for me would be what someone already mentioned on this thread; having players stats, that mark them with a number of tags that anyone can access on the lobby by clicking on the player.
Of course, for this to be viable, PD would first have to improve (a lot) on the penaly system, so people don't get erroneous info attached to their ID. Info on the number that person quitted as host would be nice.
Also, info on average finish position for drivers, etc.
With all this, someone could open a lobby, invite any friends he wants to, and still have an option for letting anyone looking for a race in that lobby, as long as it matched certain qualifications, for instance.
Another thing for people that ask for longer online races, like 10 or 20-lap races...
Do you seriously believe it would be a nice thing to have, the way things are now?
Spending a 20-lap race watching people lag everywhere, or being on the last after 30 or more minutes of hard racing, and having the host quit because he couldn't win?
That'll only be feasable (sp?) if/when PD gets dedicated servers instead of relying on some douche to host races and make everyone else depend on their mood and maturity (not to mention the stability of their connection).