Why is a raven like a writing desk?

From Wikipedia:

http://en.wikipedia.org/wiki/Alice%27s_Adventures_in_Wonderland

In Chapter 7, the Hatter gives his famous riddle without an answer: "Why is a raven like a writing desk?" Although Carroll intended the riddle to have no solution, in a new preface to the 1896 edition of Alice, he proposes several answers: "Because it can produce a few notes, though… they are very flat; and it is nevar put with the wrong end in front!" (Note the spelling of "never" as "nevar"—turning it into "raven" when inverted. This spelling, however, was "corrected" in later editions to "never" and Carroll's pun was lost). Puzzle expert Sam Loyd offered the following solutions:

• Because the notes for which they are noted are not noted for being musical notes
• Poe wrote on both
• They both have inky quills
• Bills and tales are among their characteristics
• Because they both stand on their legs, conceal their steels (steals), and ought to be made to shut up