How to Build an SMS Service

SMS Interaction Design Considerations > Intrusiveness

3.2. Intrusiveness

SMS is intrusive. Part of the attractiveness of SMS lies in its direct access to user attention. Email is filtered, snail mail glutted, but who doesn't reach immediately for their phone when the familiar chirp of an incoming message sounds?

However, attention is a limited resource, and if you squander it, you will lose the access to the very users you are trying to reach.

Many users of Dodgeball, for example, loved the service on first signing up. Establish links to a few friends, set up your phone and the next thing you know, you're receiving an SMS whenever a friend is out somewhere.

Anywhere. All the time.

What began as a fun way to meet up with friends resulted in a torrent of SMS messages, 10, 20, or 30 per night, at all hours. You're trying to sleep, and your phone is chirping and buzzing, letting you know that somewhere, people you know, or people who know somebody you know, are somewhere you're not!

It would be easy to blame your friends for prattling, but, of course, that is just blaming the user. They are only using the service as it was designed. A well designed service will channel its users into appropriate behaviors.

Dodgeball provided some mechanisms for controlling this flow (e.g., send "off" to turn off all messages for the night, "stop" to staunch the flow indefinitely, and a blocked list of friends you don't want to receive messages from temporarily), but these course controls could still leave the user frustrated. How do I get just the important messages when I want?

Twitter has begun to address this problem by creating a variety of controls for the receiver:

• Users can set "sleep" times during which they don't wish to receive any text messages.

• Users can choose to receive only direct messages (or no messages at all) as SMS (the others are read on the PC).

Some guidelines:

• When building a social networking or messaging service, establish behavioral norms through your user interface and through your syntax to coax your users to send messages to their contacts appropriately.

• Give your users a means of filtering and controlling the messages they receive.

• Users should opt-in to your service, not just out. Foisting a service on someone who doesn't want it erodes your brand and earns you nothing but ill will.

NOTE

In the U.S., SMS spam is covered by the CAN-SPAM Act of 2003 and the Telephone Consumer Protection Act of 1991.

Worldwide, laws vary. Ethics don't:

• Do not send unsolicited SMS messages to people.

• Make sure your users have an obvious and easy means of quitting your service if they so choose.

• Customers should be wooed, not tricked or shackled. Let your users opt-in and opt-out.

• Let social networks build organically. Mining address books is just nasty.