I wish people cared more about money that was spent effectively, and less about money that was given to a charity. It's not enough to just spend money on charity, as Givewell.net notes:<p><pre><code> Conventionally, most people expect that charities are
probably accomplishing good unless there's proof that
money is being misappropriated. We disagree: we think
that charities can easily fail to have impact, even when
they're doing exactly what they say they are.
</code></pre>
They've raised questions about Kiva.org's effectiveness and screening process; see <a href="http://blog.givewell.org/category/kiva/" rel="nofollow">http://blog.givewell.org/category/kiva/</a> and <a href="http://www.givewell.org/giving101/Accomplishing-Nothing" rel="nofollow">http://www.givewell.org/giving101/Accomplishing-Nothing</a>.
Microcredit is still an unproven intervention. It seems like an obviously good thing, but we have a paucity of evidence for its efficacy as a remedy for poverty. The best available randomised trials show indifferent results, with only marginally statistically significant benefits.<p><a href="http://www.cgap.org/gm/document-1.9.55766/FORUM2.pdf" rel="nofollow">http://www.cgap.org/gm/document-1.9.55766/FORUM2.pdf</a>
While a new search engine or email reinvention sounds daunting but lucrative, in my opinion the most impactful "frighteningly ambitious startup ideas" are like Kiva'.