Why sending a tweet is more cost effective than sending an SMS
Everybody knows telcos are charging excessive rates for SMS. This piece from 2008 compares the equivalent of sending MP3 files using AT&T's cost for SMS. Note that AT&T's SMS rate has gone up to USD 0.20 since that article was published.
We in Indonesia don't get charged anywhere near that much. Inter-network SMS is often free while off-network SMS only cost up to IDR 150 or USD 0.015 (US 1.5¢) and we don't get charged for receiving them although Esia charges IDR 1 per character for each SMS you send, so sending 160 characters costs IDR 160 but sending a simple Yes costs only IDR 3.
Even then, I still don't send SMS that often because there is a much more effective way to communicate. Twitter.
Indosat and Axis charge IDR 1 per Kilobyte while Telkomsel charge 5Kbps. I haven't checked other providers' rates and can't be bothered for now.
If you use a web-based Twitter client such as Mobile Tweete, or Twitter's own Mobile Twitter, each loaded page containing up to 20 tweets is only 4 KB in size which means you get charged IDR 4 for pulling down up to 20 messages if you use Indosat or Axis (which I do). The Mobile Slandr site which includes user images loads about 10-14 KB per page.
With those sites, If you send a message to the public timeline, you'll also pull down additional messages at the same time. Basically, each time you access a twitter page, it costs you IDR 4 - 14. Even using Telkomsel, loading a Twitter page costs less than half of an SMS.
Naturally, if you access Twitter from a Blackberry or an iPhone, the cost might be slightly greater as the Twitter apps pull in more data than those compact sites.
By sending a message to the public timeline, everybody who follows your Twitter account receives your message, pushing that cost down even further as you don't have to send it multiple times to reach multiple people.
Even better if you happened to subscribe to a fixed cost unlimited data package from your mobile provider, because it means the more you send, the less it costs per message even without considering that you use the data plan for other internet activities as well, which you obviously would.
True, not everyone is on Twitter but a large segment of mobile users especially Indonesian Blackberry and iPhone users are adopting Twitter as the latest trend after Facebook and it's growing quite quickly.
So what are you waiting for? Stop sending SMS and start tweeting!