Data goes in, Data comes out.

Data Portability

When you’re building a web application (you know, like Twitter, or Flickr, or Facebook, or Last.FM, or Posterous) you obviously want people to put data into it, and you’re going to make it easy to do.

But are you making it easy for people to get their data out of it?

Here’s my simple rules for building a web application:

  1. Make it easy for users to get their data into your system.
  2. Make it easy for users to get their data out of your system.

That’s it. Do number 1, then do number 2, Do not stop in between number 1 and number 2.

If you’re convinced your application is amazing, you shouldn’t have to rely on lock-in to keep people using it. They’ll praise it openly, they’ll become your fans, they’ll shout it to their friends. Anything else is bullshit.