When several dm messages are exchanged between two people (you and one other) in a short period of time, Twitter (or your client) will auto-detect and move into

When several dm messages are exchanged between two people (you and one other) in a short period of time, Twitter (or your client) will auto-detect and move into a chat mode. The 140 character limit really starts becoming a serious limitation. Perhaps you could implement this feature such that it would only trigger if both of you are on a fat (read: desktop) client so it doesn't cut off the mobile subscribers who may still depend on the 140char limit.