Twitter is currently Beta testing doubling tweet lengths to 280 character.
Twitter said the reason for he change was to eliminate what it viewed as constraints that kept people from tweeting more frequently. According to Twitter’s internal research, 140 character limit stop people from tweeting often.
“When people don’t have to cram their thoughts into 140 characters and actually have some to spare, we see more people tweeting,” Twitter said in a blog post. Check out the full story here.