If a player can get one point a second that's 2.78 hours of continuous play that would be needed to score 9999.
But how many try will it take to get pass 9998 and 9997? The precision there. I am sure someone may have that skill to do it, but it's really questionable whether all of them are legitimate or not. And in fact, are they all legitimate... the highest in real life I know is 200.
'Desert Bus' requires 8 hours to score one point...
Wow. That is hilarious. I was going to comment that it should be an Apple/Android app just for shits and giggles but after a cursory search I discovered that it already is! And it costs $1!
Hacking scoreboards is pretty easy for people who are skilled at reverse engineering. Once one of these people figures out how to do it (usually by mocking up the high score message the game sends to the server) they release their crack on Cydia, and thousands of people take advantage of it.