I don't get to use it too much as I am usually in front.
and if you are in the kart ahead then you should be aware of it and drop a banana/fire a shell. If you let the person behind do it to you then you are a fool, and if you do it to someone else then they are a fool.
Another way to avoid the person beind doing it to you (I think, I haven't tested it properly but it seems to work) is to go into a drift, If you are in a drift and the other person isn't (and vice versa) it doesn't seems to work.