We've been living with the limit imposed by Ev and Biz and Jack for a few years, but what's the magic of 140? It's pretty much a random number pulled out of the air (I know some people will say it's magic, they do that every time we question this limit. Could you just let this proxy stand in for your appeal? Probably not.)
My project: I asked the editors of the NY Times what they think the average length of a nugget of news is. I didn't sit them down and interview them. Rather I turned to their RSS feeds. I figured the actual data would do a better job of speaking for the collective. What is the consensus among NY Times editors?
I didn't include the link to the full story because I figured that any Times-based news delivery system would hide the URL as metadata, unlike Twitter (I believe this is a design mistake). I only included the title and the description. I looked at 8279 stories that had been gathered by my aggregator since September 2009 and now. I really had no idea what the number would be. If you had forced me to guess, I would have said the number would be somewhere between 250 and 500.
Even so, the answer is fairly clear. 140 is not enough, not even for the average nugget. And to be able to hold the largest one, the max would have to be 250 or 300. And there would be no room for the link, even shortened, in that size nugget.
Update: Here are the posts that were studied in this post.