1. Open chat with userA
2. Send a message "hello there" to userA
3. userA sends you a file
4. you see a notification popup "userA - hello there"

so, if you are not looking into the chat window at the moment, you can think, that this user is just saying something, but this could be a file transfer and you will miss it after some time. not to mention that this popup is just repeating any message (yours or contact's) prior to file transfer.

originally posted:
http://www.igniterealtime.org/community/thread/29222?tstart=60