Hi there,
In hope that others will find this information helpful:
when you buy anything on android market, "google wallet" will remember your credit card. This, in turn, could lead to "you've just payed 7.99€ for useless 5000 stars in 'Sheeps & Clouds' games, by letting your kid, uhm, continue to play games after you were silly enough to set up your google wallet".
Note, this thing is on by default. Note it looks like it can't be switched off, other than by removing credit card reference. (I hope at least removing it helps)
Also note, that "in-game purchases" are non-refundable.
Oh, and there is no answer from the "developer" who could, according to google, be so kind to return money he just legally scammed, pardon my French...
Not sure if it fits "news" forums, but I wish I had read such news earlier.