This is an awesome idea. I like the idea of waking up and getting an email "this is who you helped without even knowing it!".
The detractors are missing two important points:
1) People like being part of a larger movement.
2) People like knowing their donation as impact. I would rather be part of a team donating $1,000 then just donating $1.
I signed up for the free email, but if I like what I see I'll be joining.