In 2013, the UK's Office of Fair Trading launched an investigation into exactly this topic, producing a report outlining some of the "misleading commercial practices" that were aimed at "exploiting children's inexperience, vulnerability and credulity" by promoting in-app purchases.
Via The Digital Rocking Chair, Peter Mellow
Stuart Dredge: "Angry Birds maker Rovio may have seen its growth stall, but there are plenty of reasons to be excited about mobile gaming" ...