Obviously the people adding these premium numbers to the adware are to blame (they are just trying to screw the public, which is what premium rate numbers are for).
But it sounds like Apple should take some responsibility for this too. it should never have removed the "you're about to make a call" warning from the API. I can see that this box could become annoying (esp. in a game) if you keep accidentally hitting something that would initiate a call though, so apple should really add a setting along the likes of :-
1/ Pop up a box and warn that you're going to make a call
2/ Don't pop up a box - just make the call
3/ Disable the API and prevent any calls at all being made via it
That should keep everyone happy (apart from the advertisers of course because most people would select option 3 of course)