(While checking my guesses, I saw that MW will accept 'fair trader' but not 'fair-trader,' despite the fact they list 'free trade' as 'free-trade;' and you can't split a word into two if it's not in a compound, can you?)
The ways of m-w are inscrutable. I noticed that they accept both "fair-trades" and "fair-traded", but not (as drom points out) "fair-trader". At first I thought this was because they only listed "fair-trade" (with the hyphen) as a verb, but then I realized that makes no sense, because why wouldn't someone who engages in the activity of "fair-trading" be a "fair-trader"?
I suppose that the people who do write the dictionaries don't think about double spellings (hyphened and unhyphened,) at least in this case. What is exceptionally weird is dictionaries on certain mobile phones. The phones have word-banks so that one can use predictive texting, which sounds like a sensible idea. But, when they don't have the name 'Clare' or 'Castle' but do have 'myxomytosis,' things get surreal...
Inscrutable is the perfect word for it.
Would anyone like to submit the next word for the game?
In the interest of keeping things moving along, and since I'm eligible to post again under the 12-hour rule, let's see what happens from:
fair-trades
OK, then, Mac! How about
[size=7]Rib?
There is at least one word that can follow WRITABLE.