Both those references refer to your average marathon runner not to elite marathon runners.  But you are right that your average joe marathon runner probably has a terrible vertical.  It is kind of extreme example of what Steve talked about earlier in the thread, that high repetitions don't build your power.  The reason I questioned that number for elite marathon runners is because they have enough power to out sprint your average joe, like me.  For example, I have about a 22" vertical jump, and can only run a pathetic 15 second 100 meter dash, whilst someone like  Martin Lel http://www.sportsscientists.com/2008/04/london-marathon-and-speedo-lzr-news.html can run the last 400 meters of a marathon at faster than that pace. Or someone like marathon world record holder Haile Gebrselassie can run that pace for an entire 5k.  I have hard time believing people who can out sprint me when they are running at 5k pace or the end of a marathon don't have enough power to to jump within 10" of my vertical.  I guess I am just being nit-picky, but sometimes I see these factoids thrown around whose truth is taken for granted when they may in fact have no basis in reality. But anyway, yeah running a lot isn't the best thing for your vertical jump.

By factoid I merely meant there has not been any actually studies that I have seen that actually show this, just anecdotal evidence.  I would love the opportunity to do such a study.  In my counter anecdotal evidence, when I was a distance runner running 40-70 miles a week I had about a 27"  vertical.  But I pretty sure that my better vertical back then wasn't because of all the running, but because I did a lot of sprint work and I weighed about 35 lbs less.  Which brings me to a great way to improve your jumping ability if you are overweight: lose the pounds.  I had a friend (again anecdotal evidence) who lost 100 lbs. in about 6 months.  He had an incredible vertical jump after that because his legs were used to supporting a lot more weight.

I saw that study too in doing a search for theses kind of studies.  I am trying to get a hold of the full article right now to see if I can get what their actual jump heights actually were.  But no doubt about it, a long hard run will seriously impact your jumping ability in the short term.   Another very interesting study is the one discussed here: http://www.pponline.co.uk/encyc/0687.htm.  To summarize it, if found that for serious runners, jump height is very good predictor (74% accurate) of who will have a faster 10k time.  Of course this correlation is not always true, i.e. Kelly Bagget's 42" jump does not mean he could beat or even come close to Haile Gebrselassie in a 10k or that Haile Gebrselassie could out jump  Kelly Bagget.  But for two people that are serious runners the faster one probably would have a better vertical.  So for example, when I was a serious runner my fastest 10k was 37:20 and I had a vertical of 27", so , according to this study, Haile Gebrselassie, whose best 10k is 26:22, has a 74% probability of having a better vertical than me.
   My take away from these studies is this:  Running a lot will not help your jumping ability.  However, working on your jumping ability and power will have the side effect of increasing your running ability.  This idea is further confirmed by this study: http://www.ncbi.nlm.nih.gov/pubmed/18460997

I read that one too. I think we were both looking for hard evidence, and found the same things. I don't remember my 10K pr, so you're 74% more likely to have a better time.