I just launched a game with a small virtual team of three (plus myself). It was quite successful. We made some decisions like using email as our primary communication medium, and iRC as our primary chat mechanism.
Now, three other new people have joined the team. (We're an informal collection, unpaid, collaborating on a common interest.) Some of those decisions, and others, are being challenged.
I know that the right move is to remain with the decision, because I personally spent countless hours researching and reaching the same conclusion from different angles about these decisions. I cannot indulge in churn from re-opening old decisions every time someone new shows up.
So for now, the decisions are irreversible, barring unforseen circumstances.
How do I communicate this? I need ultimately to get buy-in from the team on any given decision, don't I? But it's a team of individuals with strong opinions -- some may buy in and go forward accepting it, and others may do so because it's required of them on the team, while still others may continue to challenge it at every opportunity.