Naturally, he is sure the rankings drop is temporary. That should be taken with a grain of salt, and the reasoning behind his belief is more important. To that end...
The drop was wholly due to the low employed at graduation rate. So, why did that happen?
1. Emory has only one program in place to "game" the employment statistics. It places jobless Emory grads with local employers (small/mid-sized firms and public interest) on an internship/short-term basis with an eye toward long term unemployment. It was put in place at the end of Calendar 2009, so is not reflected in the 2011 USNWR rank, which counts 2009 grads' employment stats. Other schools had similar programs in place for a year or two before this, so their programs are reflected in their employment statistics.
1a. Similarly-ranked schools have other programs to increase their employment numbers, especially employment at graduation. At least 3 schools ranked 17-30 actively employ graduates on a part-time basis, with no intention to keep them after the reporting period. At least 1 sends out emails to all jobless graduates, "offering" them a position at the school for 9 months, noting that if the graduate DOES NOT REJECT the offer, the school considers them "employed" for USNWR (which defines "employed" as having an "offer of employment").
2. Emory does not pay its unemployed graduates "bar stipends" as other schools do. This would take unemployed students studying for the bar out of the "unemployed" category.
3. USNWR reclassified all graduates seeking higher graduate education as "unemployed." This is probably the weakest reasoning, as it should affect all schools equally. However, Emory had an unusually high number of 2009 graduates who went for LLMs/PHds/MBAs/etc (numbering >10 when it normally is <5). This could also be attacked on the reasoning that these people are going for higher degrees because they couldn't find jobs, so would be counted as unemployed anyway.
4. As much as the email from Emory has been pilloried, there is something to be said for the number of Emory students who seek big firm jobs, and big firm jobs in other cities. Look at the schools that we fell behind. UMN, Iowa, IUB, UIUC, W&M, etc. Many students at these schools are committed to their regions, and are interested in jobs with small- and mid-sized firms. Emory, on the other hand, draws a larger portion of students who are seeking big firm work, and students who are seeking work in their home regions, or in DC, NY, CA, TX, etc.
In a down economy, it is much harder to find big-firm work, and particularly big-firm work outside your school's region, than it is to find local, small-firm work. This is reflected in the NLJ hiring numbers, which show Emory above every one of these schools, among others. This isn't really reflective of Emory's reputation or "hiring power," but rather the preferences of its students. Do you think a graduate from any of these schools would have an advantage over an Emory grade in getting a job in a "neutral" region (say, CA or NYC biglaw)? I hardly think so. Of course, as ATL pointed out, this argument doesn't explain why Emory should drop more than, say, Harvard, where lots of students are seeking big-firm work, but this is fallacious: the question is not, why did Emory drop relative to Harvard, but why did Emory drop relative to its peers.
What's the bottom line? The 65% number is probably accurate for at graduation employment. This reflects the number of graduates who have jobs through OCI, hustling during 2L and 3L years, and through personal connections. The remainder generally study for the bar, then apply for jobs afterwards, which is properly reflected in the 9-month number: above 90% if I recall. However, the 65% number is probably close to accurate for other schools in Emory's peer group as well. They have just done a better job "gaming" their stats. I doubt that will continue into the future.