Sure, it's easy to launch a webapp as your startup. But how will your first customers or users discover you?
A lot has been said about launching early or simple or lean. Not enough however, has been said about earliest discovery. It's sure easy to launch a startup to test when you have thousands of followers already. It's a whole other issue when you don't have any followers (not only on twitter, but everywhere on the internet.. the sum total of your audience)