Lyman,
There's lots of evidence that 1 m/km net drop provides substantial aid, at least for runners smart enough to take advantage of it. As specific articles to read, I'll start with one that wasn't in Measurement News, but rather in NRDC News, namely, the January 1986 issue available in the NRDC News archive at http://www.runscore.com/coursemeasurement/NRDCNews/ where you should read Ken Young's material. The drop limit had been set originally at 2 m/km in 1983 when rules for US Road Records were first established. But in this 1986 article, Ken recommended reducing the drop limit to 0.4 m/km, which would have made sense according to the principle that the aid provided by elevation drop shouldn't be much greater than the uncertainty in time resulting from uncertainties in measurement of the course length. Politically, however, it wasn't possible to reduce the limit lower than 1 m/km, which is the revised limit adopted in 1989.
Regarding your point about courses with a lot of uphill in addition to a net drop, I suggest reading a bunch of articles in the Measurement News archive at http://www.runscore.com/course...ent/MeasurementNews/ Start with my article "Hill Effect to Second Order" in the January 1989 issue (MN 33), then an article with the same title by Alan Jones in July 1989 (MN 36), and also the article "Uphills, Downhills and the Boston Marathon" by Alan Jones and myself in March 1990 (MN 40) -- and see also Pete's "PACE CHART FOR BOSTON MARATHON" in that issue. For still more comments, see my article "Understanding Aidedness--The Effect of Drop" in March 1991 (MN 46). All of these calculations show that, for most courses, the effect of the uphills doesn't significantly reduce the aid provided by the net drop.
Your comments about "margin of error" reminded me of our debates in the 1980s (in a different context) about "Allowance for Error in the Validation Measurement" (AEVM). In that case, RRTC adopted a policy (announced by Pete Riegel in Nov 1989 Measurement News - MN 38) that a course would "pass" validation if the remeasurement came out short by as much as 0.05%. That AEVM was thrown out in 2007, when RRTC's validation procedures were modified to match those of IAAF.
When considering the science on any of these topics, the situation tends to be somewhat fuzzy, and we may often express uncertainties using two-sided (plus or minus) tolerances. However, for the purpose of record keeping in athletics, although the rules acknowledge measurement uncertainties, tolerances are always one-sided: Field event implements must weigh at least the amounts specified; courses must be at least as long as stated; and in the case of elevation drop, the drop must not exceed a specified limit. The official rules relating drop to record eligibility are:
USATF Rule 265.5(a): The course must not have a net decrease in elevation from start to finish exceeding 1 part per thousand (i.e., 1m per km).
IAAF Rule 260.28(c): The overall decrease in elevation between the start and finish shall not exceed 1:1000, i.e. 1m per km.
The USATF rule has been on the books since 1989 and the IAAF rule nearly as long (since IAAF began keeping world road records). We can't expect these rules to be changed. We've realized now that the elevation data we customarily obtain isn't always adequate to determine unambiguously whether a course's drop is less than or greater than the 1 m/km limit. In such cases, if record considerations arise, we must simply do our best to obtain better elevation data and try to determine whether the course meets the record eligibility criterion.