The scenario I worry about is that, under the futarchy mechanism,
someone (call her Alice) makes a deliberately obscure self-serving
proposal.  Since other traders can't easily figure out what they're
trading, they are scared off, turning the market into a non-market.
Since no-one else is trading, Alice's bid or her trade with a
confederate effectively dictates the price.  She sets a price
sufficiently high to enact her self-serving proposal.

Of course that's a simplified version that doesn't consider
counter-rules and countermoves to those rules.  Other than what I
proposed wrt controlled language, I believe most counter-rules are
defeatable, but we can talk about that another time.

Here's a version with more detail:

Alice proposes the following:

	Enact the proposal described in the plaintext corresponding to
	this cyphertext #..dkegs4fr inscrutable cyphertext here
	df4ix5ufh ..# as decrypted by an asymmetric RSA key whose
	public component is #...PGP key here..#".

Of course only Alice knows what the proposal says.  By revealing the
corresponding private key later, she can reveal the corresponding
plaintext at a time of her choosing, or never reveal it at all.

Alice repeats this procedure with different keys upon a mix of
proposals, some of which are identical to promising recent proposals,
some of which are pure "gimme"s diverting public resources to her own
interests.

To the general public, these opaque proposals appear all essentially
the same.

Before revealing a proposal's content, she buys "yes" shares in it.
Regardless whether others will trade with her, she does well.  If many
do, she holds a fair amount of "yes" purchased at a moderate price
(unless the price is already higher than that, which diminishes her
profit on her "clones" but brings her that much closer to enacting her
"gimme"s) If nobody at all will trade, she effectively dictates the
price.  If just a few do, she has a mix of the two benefits.

When a "gimme" issue's price rises high enough to cause it to be
enacted, she reveals it.  She also sporadically reveals some "clone"
proposals and cashes in on the subsequent rise in price - presumably
up to the level of the claim it's a clone of.  If it doesn't rise in
price - perhaps she is boycotted - she wins anyways when the real
original claim is enacted.

This does not exhaust Alice's possible tricks.  She could also clone
some unpromising ones, thus defeating any counterstrategy that's based
on public knowledge that she wants all her proposals priced high.  But
I've written enough that you can see that.