Speed.
Yes i support your thread. I was against clans in D2, becouse, system force me to create new character with clan tag, wasting my time... And now, if Blizzard implemented clan features, there will be tag upon your nick char for example. No more new accounts and characters. If u quit or they will kick u, tag will disappear.
Another thing is about limit of people in clan structure. There should be limit like 12 ppl in - no more.