Fred Wilson recently posted about the importance of SMS as a mobile interface, saying that in the debate between web apps and mobile apps on phones, you should not ignore the least common denominator, SMS.
I believe that Twitter’s native implementation of sms is an important part of its success. The 140 character limit was driven by the 160 character limit of sms and the initial design of the service put sms compatibility up there near or at the top of the system requirements. Other competitive services, including Facebook, are just not as natively available via sms the way Twitter is.
In general, I agree.
However, he also notes that:
Of course most people access Twitter and Facebook and other web services via mobile web interfaces and apps. I don’t know the current percentages but I think something less than 15 percent of Twitter updates are posted via sms. And the number of people following via sms is also relatively low.
I”m sure a lot more than 15% of Twitterers tweet some of the time via SMS, so the 140 character limit has its benefits for making it easy to tweet. However, I think that there is another very important advantage to limiting tweets to 140 characters, and that is that it keeps the cost of spam down.
Many people have complained that Twitter is getting spammy, and that as a user follows more twitterers, they see a decrease in the signal-to-noise ratio in their feed. Obviously, it is always better to have a high ratio of signal-to-noise.
But if the “cost” of noise is low, then you can tolerate more noise. Twitter’s 140 character limit helps keep the “cost” of noise low; it is easy to scan the feed and skip over tweets that are not interesting to you. Since Twitter has few ways to filter the feed to minimize noise, short tweets are important to reading as well.