Loading is, as Dover pointed out, so much dependent on not just the cartridge, but the particular phonostage, that a very specific manufacturer recommendation would not make sense (hence, the wide range Dover mentioned that VDH recommended). I think manufacturer's sometimes make a recommendation just to prevent customer angst and endless inquiries. The 100 ohms mentioned is an almost universal recommended loading (it works well enough for the vast majority of MC cartridges) and is a common figure for MC phonostages that have fixed loading, so it is not surprising that VDH included that figure in his recommended range.
From my own experience, I generally like wide open with essentially no loading (47k is pretty much unloaded). The 500 to 1k that VDH recommends on their website for the Colibre is pretty much unloaded too (I bet few can actually hear a difference between 1k and 47k). If one really "needs" to load below 100 ohms, something is unbalanced with the system/setup. I own a Transfiguration Orpheus L. It has a source impedance of 1 ohm. If one used the 10X formula that some recommend (like Fremer), the proper loading is 10 ohms. That would make the cartridge sound sodden and shut down and would seriously reduce the output of a cartridge that is already somewhat low in output. With something like the Colibri, one is paying big bucks for the spectacularly open, and fast top end of that cartridge--it would be a pity to wipe that all away with excessive loading.
Atmasphere's comments are consistent with what some cartridge manufacturer's have said--loading may be helpful when there are issues with RFI and where the ultrasonic resonangt peak of MC cartridges may overload a phonostage with poor headroom margin. A friend had noise problems with his Hovland HP-200 (caused by RFI). It turns out that the factory default setting is 100k. When we loaded it to 47k, the problem went away.
