Ive seen people sending messages via micro payments ig.    00100101010 are they just typing that in?

On blockchain.info they have an option for "Public Notes" it looks like adding micro coins on my transaction as well.  EDIT- there is no micro 10101 on this, I was mistaken.

what applications have you seen this in use? I more interested in eCommerence examples rather then anonymous messaging.

Could this be used a receipt signing? maybe even to keep track of inventory or sales? Merchant scans a product and signs the request BTC with product number?

If you were to make an app, could you use this messaging a type of handshake to verify payments?  

ig user A sends bitcoin to B. However C says it was his payment and contests transaction with B. If there was a handshake between A and B could add security.

doing some brainstorming.