If someone barely missed passing through 1st round, chance for him to make it through any of the following rounds is practically non-existant. Exception being if he's experienced competitor who fell short for some reason.
Well, it will only be the last 3 spots that are (substantially) affected by 3 cheaters - everybody else either qualified or failed to qualify anyway.
And the luck I'm referring to is in timing. If you look at the scoreboard for round 1B, 1000th place scored 34 points and a time of 1:30:38. 1001st place 34 points and a time of 1:30:48.
Imagine this scenario ,It is round 1C . A talented programmer started competing there are only 20 minutes to go. He solves the Small and Large test cases for Problem A ,and only the small for problem C. But Alas ! his rank is 1002 , he doesn't qualify even though on topcoder he is in the top 200's.