Most strikingly, even though it doesn't put much emphasis on grades, and its students supposedly smoke a lot of dope, it's also notoriously hard for a liberal arts college.
So, lots of people don't graduate. A famous Reed dropout is Steve Jobs, the CEO of Apple and billionaire. A not famous Reed dropout is my cousin Joe, the farmer and thousandaire.
Being hard hurts Reed in the USNWR rankings, because percentage of students graduating is entered as a positive variable in the formula. While over 95% of entering freshman graduate from the three most highly ranked liberal arts colleges, Williams, Amherst, and Swarthmore, only 73% graduate from Reed, which contributes to its #53 ranking by USNWR. Reed freshmen have virtually the same SAT scores (1280 at the 25th percentile, 1470 at the 75th percentile) as #5 Middlebury, but 94% of Middlebury students graduate. Demonstrating Reed's iconoclasm, the president of Reed, Colin Diver, even wrote an op-ed in the NYT in 2004 in praise of the SAT. Practically every president of an elite college depends heavily upon the SAT (and/or the Midwestern ACT), but seeing them admit that in the NYT is, well, unlikely.