MOD: Gents, for the sake of avoiding a faeces throwing episode, can we keep it civil. This could be a great brewing discussion if done correctly. Anything resembling a personal attack or provocation to commit same will be removed and warnings issued. Not saying it's there, but just a warning to keep it on the level.
For my part, I should have been more descriptive as to my disagreement on a brewing basis, which I will now do:
Pitching onto a yeast cake does work. But like all yeast based exercises, it's a matter of getting the right colony for the right job. As we are dealing in relatively (relative to the professionals) micro batch exercises, and therefore our results can wildly vary. My experience with Hefe beers, is that an underpitch works. If that's from a yeast cake, it is simply take an 'underpitch' quantity from the yeast cake and go and pitch that. But like all micro-level home brew exercises, it might take some experimenting to work a system that is the equivalent of millennia old breweries standard system.
My honest opinion re: Hefe beers is, rather than pitching on a yeast cake. Get hold of a sachet/smack pack. Build a yeast colony where you can freeze/save the split colony (the 'let's freeze some yeast' thread is awesome) to cover costs. That way, you can use Mr Malty and start from a basis where a guessed quantifiable amount of yeast can be obtained. And it's cheap.
For my yeast cake beers - I did the above with the split colony. After splitting the colony, one vial was used. Pitched a low grav beer, fermented out, and then the higher grav beer when onto the yeast cake. Easy enough. And a $2.50 vial was used for 2 beers, with results being what I expected and wanted.