Uhh … me?
I applied to both Carleton and Reed and was accepted at both schools. In fact, they ended up being my top two choices because they were the only two schools that had everything I was looking for. They’re really not THAT different. In fact, I feel they are actually more alike than not. You can certainly find other schools that are much, much, much more culturally dissimilar. I might even go as far as to say that Reed is probably the closest thing to Carleton you can find in the Pacific Northwest.
I’ve returned to Carleton every few years or so since graduation, both during the school year and during reunion. My most recent visit was in the middle of spring term 2015. I also visited Reed last fall. Perhaps I caught them on an exceptionally boring day, but I did not see, hear or smell anything on the Reed campus that you would not see, hear or smell at Carleton.
Incidentally, I was definitely not alone in applying to both places. One of the schools (can’t remember which one, maybe both) sent something to me that showed the other as being one of the schools to which kids most often applied. So, apparently, there’s a non-insignificant overlap in the applicant pools of both colleges.
In any case, you probably don’t want all the schools on your list to be TOO similar. That could be just as bad as having a very disparate list. If the admissions departments are looking for the same things, you risk being rejected by all of them. (E.g., see what happened to this person: http://talk.qa.collegeconfidential.com/college-admissions/1891200-asian-rejected-from-everywhere-postmortem-p1.html)