You guys put too much emphasis on the away rotations. Not everyone can do aways at every place.
The reason why a lot of people match at one of their rotations has little to do with the fact that it 'enhanced' their chances of getting in.
consider the following:
If you do an away rotation, you either really like it, or dislike it.
In the beginning, one of the reasons you rotated their was because you liked aspects of the program that matched your life (ie location, lifestyle, whatever). You liked it before you went there. No one says, ahh what a lousy place, I'm going to spend a month there, that sounds like a great idea! You also pick your aways based on the strategy of "I think I could match there, realistically".
So, in the end, you're going to rank it either at the top, or far down your rank list.
It's natural human psychology to go with the familar. Let's say you interview with 10 programs. You don't really know the programs..and even if you thought you did, you will never trust your judgement as much as your experience that you had from you away. So, chances are, even if a place was steller, if you liked the place where you rotated, you still would rank your rotated place higher. You trust the familar. The only exception are your 'reach' places.. like the places you got interviews at that you never thought you would match at. In that case, you're going to rank those higher than your away rotation, but you're less likely to match there in the beginning because it is a 'reach'.
..and then at the end of it..the program knows you better, and trusts you, so you may have someone stick out their neck for you (that knows you from rotating..).
So it all adds up in the end, but it really has little to do with the concept of 'I have to rotate somewhere to get in'.. It really isn't the case.