I read a bit old article that was posted April 2010.

• 9歳の息子がDropboxの更新通知を使ってチャットしてきたぁ

He was sharing documents with his son by Dropbox. Someday his 9 year-old son created a new document and then change the filename like “Hey.doc”. He got pop-up notification from Dropbox. His son kept changing the filename like this - “Dad.doc” -> “That sucks.doc” -> “When I login.doc” -> “It shows 5 minuites remaining for play.doc”.

His son was using update notification as alternative of IM. I’ve never thought if it can be used for chat.

After that, they chatted in a text file instead of changing filename. He wrote the post with the chat log which is stored as updated history of those files in Dropbox.