Most of "little" brand (chinese brand but also european/american brand) are writing IMEI on the box.
Telling it on a forum is not a great idea, but telling it to one guy is not more dangerous than putting your box in the bin ^^
You still have your phone with the warranty and bill in case of problem with IMEI the manufacture will repair it
Doing a quick search on it, seems to show that yes there is a risk of some other phone being found with the same IMEI. Not a lot of people keep their bills after buying the phone, so its still sort of a risk incase the phone is used to do something illegal.