All true, but the schematics indicates a 150µA load, dutifully taken into consideration.
Plus I do not expect anything close to a µA o.o.m. leakage from a ceramic 100nF cap...Ma dove li compri condensatori così scamuffi? 
A 56
resistor with no load (or a light one) would force 0.8/56 ~ 14 mA through the LM336 - exceeding recommended operating conditions.
I was misled by the polarized capacitor symbol (with reverse polarity) and that led me to think it was a 100 µF capacitor...

I would not trust much such schematic...
You're right about the LM336 limit... I forgot to check the datasheet

I think it is better to provide some more information to beginners so one may understand how circuits work and when such information is wrong (like the oversight on LM336 current of my example) somebody would correct that
