As you may be aware, BlockChalk lets you “reply” to other people’s chalks. Replies enable you to carry on private conversations with other BlockChalk users, even though there’s no registration or sign-in. It’s really useful for things like making contact with a seller and taking a transaction offline. Of course there are many other uses, and since BlockChalk launched we’ve noticed that people are replying quite a lot — almost 1/5 of all the posts to date are BlockChalk are private replies.

We’ve heard from a number of people that they like private replies but would also like an easier way to reply publicly to someone else’s chalk. So today we’ve introduced a new feature called chalkback. Now when you’re reading a chalk, you can tap “chalkback” to post a public response. Everyone in the area will see your chalkback, along with a link to the original chalk you referenced.

Chalkbacks are available for use right now on your iPhone and Android phone, and will be coming to the Palm Pre application soon. Check it out and let us know what you think.

—Stephen and Dave