I personally don't believe it works, but others have seemed to have good luck with it.
However, there is no way to prove one way or the other if it works or not. If you put up a picture and the clowns happen to be hosted shortly after that you have no idea of knowing if they were about to be hosted anyways. There is no way to run an experiment, since each clown(s) is/are different.
All I know is that I have never done it, and all my clowns have been hosted by anemones. Some took hours, others took days, others took weeks, etc.