You want to buy a new DS game for your DSi so you hop on ebay to have a look. The game that you are looking for is there alright, but many listings have told that this game won't work on a DSi. Have you noticed that most of the listing that said that are actually from Hong Kong? Because the offical Nintendo website (Austraila, UK, Japan, US etc.) say that ALL DS games will work on a DSi. The Nintendo helpline says so too and even the manual for the DSi says it. 

Here a good scenario: One time I was searching for "harvest moon DS cute" on ebay. And sure enough it was there. I recieved some Hong Kong listings saying "This won't work on a DSi." So I brought the game from the United States and guess what? The game DID work on my DSi and I've nearly beaten the game too.

This is possible due to the DSi being region free.

Who ever says that a certain DS game won't work on a DSi, is cleary selling you a fake! The DSi actually will not play a fake game.It won't even start the fake game up. That's is why they say it won't work on a DSi, to cover the fact that the game they're selling is fake. I've even seen listings saying that a certain DS game won't work on a DS lite. We all know that, that piece of fact is rubbish as the DS lite is as nearly as the same as the Original DS.

Don't let listings like that fool you. Beware.