Nate, if you get accepted, you are accepted no matter how many kids also take the offer. They don't take the offer away! The thing is, colleges offer admissions to a certain number of applicants to yield a final number of matriculants. They do this based on studying results from prior years. For instance, let's say that last year they accepted 20 but 15 wanted to come (this is a made up example) but they really only would like a class of 12. So, then the next year, they might revise their acceptances to accept 16 to yield 12. Or let's say one year they accept 14 to yield 12 but only get 8 to come, so the next year they might accept a little more to result in their ideal number. That is a simplified example.
But usually they will study patterns over a few years and know about what number they need to accept to yield the number that will finally enroll. For instance, I believe that CAP21 usually accepts 80 to yield 64 but in my D's year, all 80 chose to enroll so that the following year, I believe they might have lowered how many they accepted to yield 64 and if need be, a program can then go to the waitlist if al the slots are not filled. I know that CMU ONLY accepts the total number they want (no extra) and THEN if someone doesn't accept, they turn to the priority waitlist (my D was on that waitlist and I know how that works there). They truly don't want to risk having more than 10 MT kids (their usual freshmen class) matriculate. At UMich, two years ago, the director was explaining an earlier year when they accepted a certain number to yield 20 but more accepted the offer than they had predicted and the class was bigger than planned and so for my D's year, they were going to accept a smaller numbe , about 12 girls and 12 boys, to yield 20 and then if that didn't yield 20, go to the waitlist, rather than risk getting too large a freshmen class again.
It seems that in the last couple of years, the yield is up at several programs and they have had to revise the total number they will accept to get their class and be more conservative since so many seem to be accepting the offers, and then if they are low, they can go to the waitlist. So, the bottom line is that the schools have figured out a number that they need to accept to yield the number they want. Some schools accept more than they need and go by the patterns of the last few years and their numbers/yield and hope it will be about similar again or some might only accept the number they need to fill the slots and then resort to a waitlist if it is not filled by those who got offers. I recall several kids getting off the waitlist last year at CCM for example. My guess is that they did not initially put out more offers than spots and waited to see what students would do and used the waitlist in cases when students didn't take a few slots.
NO matter what....if you are offered a spot...it is yours!

They do not take the offer of admission away and yes, they still take you as long as you reply with a deposit by the deadline which nationally is May 1.