The reason for the Ivy League schools being so high is, as someone mentioned, their early (very early) success. Number of national titles is a criteria used in these rankings. Princeton has 24 NC's between 1869 and 1935. Yale has 19 NC's between 1874 and 1909. Harvard has 10 NC's between 1875 and 1919. This site also takes winning percentage into account for their rankings and all of those schools are holding their own in Ivy league play.
What's interesting to note is that as much as the high rankings of the Ivey League schools can be attributed to early success, Miami's high ranking can be attributed to reletively recent success. Two teams that surprise me are Minnesota and Pittsburgh being so high. I know they have solid programs, but I would have never guessed they'd be so highly ranked.
