Why is a Raven like a Writing-desk?

Riddles: impossible to dislike. In Alice in Wonderland, the Mad Hatter poses the riddle to Alice: Why is a raven like a writing-desk?

Lewis Carroll doesn't provide an answer in the book and it was never his intention that there should be an answer. However, he later wrote that the answer is, "Because it can produce a few notes, tho they are very flat; and it is never put with the wrong end in front!" Carroll also wrote never as "nevar," which is raven spelled backwards but the clever pun was erased by a proofreader. Frankly it's a pretty weak answer anyway. In my opinion, he should have let it remain unanswered, like the writers responding to "what happened to Tony Soprano at the end?" with "It’s for people to decide for themselves."

Want some more riddles?

I speak without a mouth and hear without ears. I have no body, but I come alive with wind. What am I?

You see a boat filled with people. It has not sunk, but when you look again you don’t see a single person on the boat. Why?

An 18th century classic:

As I was going to St. Ives,
I met a man with seven wives,
Each wife had seven sacks,
Each sack had seven cats,
Each cat had seven kits:

Kits, cats, sacks, and wives,
How many were there going to St. Ives? 

In Sophocles’ Oedipus Rex, Oedipus must answer to the Sphinx to save his own life and continue his journey to Thebes. The Sphinx asks: "What walks on four feet in the morning, two in the afternoon and three at night?" If Oedipus answers incorrectly, she eats him. Fortunately he gets it: “Man: as an infant, he crawls on all fours; as an adult, he walks on two legs and; in old age, he uses a 'walking' stick.” Honestly, that's an unsatisfactory literary trick.

I'm re-reading Alice, as a contrast to some heavy stuff I've been ploughing through recently, such as Mao's Great Famine. A bit like relaxing to a Beatles song after listening to Mahler's 2nd Symphony.

Wait, you want answers? OK:

An Echo.

All the people were married.

One.