What would be Dumbledore's boggart ?

[pforparvati]

No: HPFGUIDX 153229

I don't know whether this has been already discussed here, but I wonder 
what would be Dumbledore's boggart? This question has been asked to 
JKR to which her answer was:

JKR: I can't answer that either, but for theories you should read six 
again. There you go.
[http://www.quick-quote-quill.org/articles/2005/0705-tlc_mugglenet-
anelli-2.htm ]
 
I wonder where in boox six she has hinted it and what others in the 
group have to say on this...

PP