I have a couple of points to make about the improper use of statistics here. Many of the comparisons between the men's and women's standard make the statistical assumption that both men's and women's marathon performances follow a standard normal distribution (the bell curve), which is quite obviously not the case. As many of you have so subtly and delicately pointed out, there is not the depth at the highest levels of the elite women's field that there is for the men. All assumptions as to why this is the case aside (ranging from valid points that women don't have the same marathon history--first Olympic marathon in 1984--to the inherent laziness of women), it is, empirically, the case.
Because of this positively skewed distribution on the women's side, comparisons between the men's and women's A and B standards cannot follow either a straight linear comparison (i.e. men's standards x or y minutes slower than the world record, so therefore the same should be true for women), or a slightly better but still incorrect use of percentage differences (i.e. men's standards x and y % slower than the WR, so therefore the same should be true for men). The best way to EQUATE the two standards is to simply see how many athletes of each gender qualify for each standard. If more men than women make the A standard, then to EQUATE the two one must either make the men's standard tougher or the women's standard "softer." If more women make the B standard (in 2008, the total fields were not that far off in number: about 140 vs. 166, I think I read in one of the posts), then one would have to drop the women's standard slightly to result in equal field sizes.
That being said, the whole questions seems odd. Why compare the men's and women's standards at all? A better question is: what is the goal of running the Olympic Marathon Trials? The men may have a different answer than the women. Possible reasons are: 1)to choose the Olympic team, 2)to set high standards for elite status, 3)to make money for any number of parties, or 4)to encourage participation at the highest levels. Depending on the answer to that questions, the field sizes will vary.
One final point: why are we comparing the women's standards by using the men's standards as the "gold standard," meaning that the men's standards are the proper way to set time cut-offs for the Trials. Why are we not comparing the men's standards to the women's standards?