Having a 4 year old son I am the first person to put my hand up and say I absolutely HATE ads and general in-app purchases for games that he likes to play on my iPhone. In some cases the way these are implemented it is almost akin to being in a casino which is not a skill I really want my son picking up (watch this ad to see what prize you can WIN etc). I welcome Sega's announcement and will be delighted to hand over…
Maybe get your four year old a cheap Android phone or tablet and some Humble Bundled games? Then you won't have ads, and if your child breaks the device, at least it wasn't your iPhone.