popsider,
as I state at the bottom, I'm not saying that this presented evidence is correct but I'm just printing it as my understanding having read the quoted sources
Having read both JL Parker (HR training for the Compleat Idiot), and Noakes (Lore of Running - P301) on Basing and Sharpening, there is no doubt that speed work is necessary for peak performance. However, Noakes suggests a long period of Long Slow Distance running, ie, at 60-70%WHR (JL Parker), followed by a short period (8weeks pre-race) of sharpening, ie, high intensity, low-volume to build speed on top of a strong aerobic base. Both these sources appear to complement each other in theory, but there are contradictions. Parker suggests some speed training throughout the week all the time in the main schedules. Noakes suggests no speed training during the base training stage. I think this is because Noakes is really targeting the higher levels of performance runner who run a limited number of races per year and at set times of the year so they have time to fit base training into their schedule as they're not racing every w/e or so, whilst I think Parker suggests *some* speed training throughout for us mortals that run every w/e or so.
Thats the evidence. As above, I'm not saying that its necessarily correct, but I present it here anyway and quote the sources.
(John L Parker - Heart Rate Training for the Compleat Idiot)
(Tim Noakes, MD - The Lore of Running