This is not an actual problem.We disagree there. It's annoyance waiting to be solved. Here's a hypothetical, realistic interaction, and as a bonus, one that isn't any less useful due to the length limit:
>>@friend: Want to catch lunch today?
@friend: Sure, I'll set that up. Cya there!
@restaurant Reserve a table for 2 at noon for Karunamon
>>@restaurant: Confirmed, we'll see you at noon!
@traffic: How's the traffic between here and @restaurant?
>>@traffic: ETA 35 minutes, heavy traffic and construction along the optimal route.
@restaurant Change that last reservation to 12:30
>>@restaurant: Confirmed, your noon reservation has been moved to 12:30
@uber Pickup my location to the closest @restaurant
>>@uber: Driver is on its way. ETA: 5 minutes. Look for a grey Subaru, plates 1234-56.
@friend: Catching a ride there, see you in half an hour!
And this is pure user interaction, which is the least efficient way to do things possible. If you can't think up a usage for a widespread pub/sub notification system, kindly get your imagination serviced.
As far as the limit, it's up for revision by the sound of things anyways - and keep in mind the original purpose of that limitation was so a tweet would fit into an SMS. If the limit is what you think breaks this idea, you've disqualified SMS by the same rubric.
