New RAB theory...

[pippin_999]

Carolyn:
> However, he could easily have become a DE supporter subsequently, and 
> then thought better of it once he saw where Voldemort was going. No 
> idea how he could have discovered the cave, but still think he would be 
> in a better position to work it out than a scared teenager. Also, would 
> be able to command Kreacher, so that part of the second-helper theory 
> holds up.


Pippin:
Regulus died in 1959. It's either too early or too late, I think. Too early
for someone attracted to Voldemort's public platform, because LV hadn't yet
established it, and too late for one of his early cronies--they would have 
discovered his true nature (and given themselves away if they couldn't
stomach it) long since. 

I think it's a red herring. JKR loves to tempt her readers into making
the same mistakes her characters do, in this case underestimating youth.
If Harry is going to discover and destroy all the remaining horcruxes,
it lends credibility to the story that another young person was able to
accomplish at least part of the task.

Pippin