I discovered Anonymous Postcard via a tweet from @MarsPhoenix. What does AP do? From the FAQ:

Anyone who wants to express feedback to any third party submits a claim. Claims can take the form of praise, suggestions or criticism. We process the most compelling claims by turning them into postcards and then figure out the best person to send them to. We post images of what we sent along with the original claim in the gallery.

What does it look like in practice?

To: His Excellency Mr Robert Mugabe, Harare

Claim:

Congratulations on ending the cholera epidemic in Zimbabwe! Let’s toast the occasion together with a glass of local tap water!

(By the way, we’re glad to see the new house has been completed.)

Resulting postcard:

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To: The City of London

Claim:

I counted 36 cranes on your skyline on October 17, 2008. That’s too many.

Result:

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