<p>I gave a couple of examples.  One would be financial or merit aid that may or may not be available after May 1 when students have been offered money send in their acceptances.  If there is some money left over, and it is offered to a student, that could make the difference.  My son fell into that category this past year.  </p>
<p>Another would be an acceptance into a school, but not a specific program, but the possibility of spots opening after May1. </p>
<p>Other reasons can be personal family issues that may not be resolved by May but could be over the summer.</p>
<p>I say this because I know some kids who got burned that way.  They lost scholarships and their seats to schools when circumstances change, and they had made a decision on May 1 that was no longer wise. </p>
<p>As Sybbie and 1travlr have pointed out, there are ethical issues about doing this.  They have given some good reasons why a student should not hold onto to multiple seats.  However, if there if the needs of an individual trump those considerations, unless the college or high school has rules about this process, it is something that one can do.  That is the fact of the matter.</p>
<p>When I applied to colleges more than 30 years ago, I got grumbles for applying to a handful of selective schools instead of the standard 1-3 schools that was the norm for my school those days.  I was flat out told that I was going to be taking up seats that could have gone to others by applying to do many schools.  Now the norm is applying to more schools than I did.  </p>
<p>When I studied for SATs 30 years ago, I was told that you could not raise your score much by prepping and it was pretty much a waste of time other than a once over to familiarize myself with the test.  Now test prep is not only advised, but pushed by the high school counselors.</p>
<p>When you applied ED in my day, it was considered catastrophic if you backed out.  Now I see kids applying ED with no regard to the possiblility that the finances will not work out and they use that loophole to get out of ED.  </p>
<p>It used to be that very few kids used college counselors.  Now in the more competitive areas, it is becoming common place.  </p>
<p>Things have changed over time.  As said before, there is a summer melt figure built into the acceptances, so it is not aways true, not quite true that someone is taking up someone’s spot anymore than a top student who applies to multiple colleges  and gets a number of offers.  </p>
<p>On the other hand, to be prolonging the process to the very end is not beneficial to anyone many times.  The May 1 deadline forces a decision that otherwise might be held off until the day the kid has to report to college.  And indeed kids have held off that long.</p>