There is a few region locked games. Those are called "DSi Enhanced" on PlayAsia shop - http://www.play-asia.com/paOS-13-71-9g-49-en-70-3uvf.html What exactly "DSi Enhanced" means - http://www.play-asia.com/paOS-00-3-dsienhanced-49-en.html
There is also problem with region protection on DSi. Even if they release the game in US there is not possible to play it on EU DSi. The same goes for JAP release which i cannot play on EU DSi..