I _love_ the idea of getting a daily email that tells you about a worthy nonprofit that you might not otherwise hear about, and this system makes it dead-simple to make micro-donations to each charity. However, I _hate_ the idea of donating to a black box. True, Dollar a Day publishes its criteria for selecting nonprofits, but those criteria are highly subjective. And, according to the FAQ, there's no way to opt out…
A useful feature might be the ability to opt out by category or keyword. Maybe I'm not interested in animal charities, or maybe abortion is against my religion, or maybe I don't trust any charity with the word "global" in its name for some petty reason. Whatever it is, I need to be able to opt in to funding the 29 charities I'm cool with and opt out of the one I don't like.