I don't think applying to backup aways will hamstring you. I applied and was accepted to 4 aways, I only ended up doing one away and I was offered interviews at two of the aways I canceled, both of which were in California. I go to a midwest state school so based on my experience it should not hurt you too much. Take all advice you get from other med students (like me) with a grain of salt as we really do not know what goes on behind the closed doors of the selection committees.

I think that whether or not programs get offended is very program dependent. I did not get an interview at the one away I turned down, and I know of several of my classmates who had similar issues with different programs. Every program will be different, but I would suggest you apply early to the ones you really want, and if you get them great. Have the other applications filled out and ready to go in case for some reason you don't get the away you want. Also, some schools have the dates the render their decisions about who they're accepting for aways online, so it might be helpful to check those out and maybe apply to ones that will let you know sooner first, that way if their spots are filled up, you can still apply to different ones.

There is a lot of talk about some programs not offering interviews to all students who rotate through their programs. However, I would suggest that you consider rotating at the programs where you truly want to go, regardless of whether the programs interview all rotators or not. My rationale is this. On an away rotation, you basically have a month long interview, so if you get an interview after that time, great job, and you are in a great position for the interview since they know you and your work product. If you don't get an interview after your away rotation, I am sure it can be a real gut check. However, I would much rather a program NOT give me an "automatic interview" if they are not going to rank me after the interview or if they would rank me at the bottom of their rank list. Interviews are expensive, time-consuming and there is a significant opportunity cost in terms of sacrificing opportunities to interview at other programs due to date conflicts. I am sure it is difficult to spend a whole month at a program and not get an interview. However, if you rotate and don't receive an interview, in a way it is good thing since the program is not wasting your time and money by automatically bringing you back for an interview if they truly do not intend on ranking you highly.

I agree with the above statement, but not really.
Most places that don't interview all the rotators, don't interview people becaue they did not like them or they did not work hard enough. They simply don't interview all the rotators, becaue they don't have enough room to interview all of them. And they want to interview other well qualified applicants (super stars) that did not necessarily rotate there. So it comes down to: they liked the other rotator just a slight bit more than this one. There is no science, it is all subjective. Maybe if you walk the other way one day and meet/don't meet a certain resident/attending, say/don't say a certain word/phrase, it would be all different for you.
But clearly, if you spend a month there and even if someone liked you a little less than that other guy, come the interview day, you still have a chance to impress the heck out of everyone on that pannel, even people that were not that impressed with you initially. Interview performance goes a long way.
In addition to that. People that rotate and then interview statistically are ranked much higher than everybody else. So after a rotation and an interview you have about 1/3 chance of matching at a particular program.
So yes, it does matter.
Even if you did not impress that one person that one time. If a program interviews all the rotators, you have a lot more chance of matching at that program should you come back for an interview.
It is usually way more expensive to spend a month rotating somewhere than just flying for an interview.
I agree that you should rotate at place you really want to go, but this is so improbable to predict. You might love the place before you go there and then hate it after a rotation, and vise versa.
But anyways. Go to a place you "really really want to go" and rotate there. But if you have a choice between 2 places or 3 places and both/all are equally attractive. Then go to a place that interviews ALL rotators.
Email their rotation coordinator and simply ask before you apply.
Why waiste precious 1 month and about 1,000-2,000 knowing you might not get an interview there. You rotate not just for experience. You rotate to get your foot in the door, and to hopefully get in, come the match day.

Bottom Line is rotate where you think you want to end up and don't let the fact that a program does not interview all rotators dissuade you from rotating there, especially if it is your dream program. In response to the poster's original question...I agree with BoneDoc and BillCutting who summed up some of the important issues quite nicely. Another consideration is to rotate in a region to show interest and open up interview opportunities geographically. I believe Chicago has historically been quite difficult to get into, so if you are interested in that area, you may consider rotating at a program there.