As I think you would agree, if not say explicitly yourself, the real issue is the quality of SOPW node titles, and you are testing the idea that a title with two or more words is generally better than a title of just a single word.

And I would have to concur, even though plenty of useless but wordy node titles spring to mind.

But in keeping with the cost/benefit approach, let me list off some more of the possible costs for consideration.

1. It might give a false impression of mistrust, especially to Initiates.
2. It reduces freedom of expression. Here's a question - does the PM community hold the view that node quality is related to freedom of expression, albeit sometimes warty expression?
3. It could be annoying to have your entitling hand so forced. Say, for the sake of argument, someone writes a node asking about splitting words from a sentence with no whitespace - SomethingLikeThisForExample. SmartyMonk might want to entitle that node along similar lines, but wouldn't be allowed under the proposed prohibition.
4. It might foster a new, possibly even worse mutation of poor node titles, where spaces are added arb itrar ily, just to circum vent the guard ian RegEx.

Now admittedly these are fairly intangible costs, but then that is the nature of quality. And a small gain in node-title quality could cost us in terms of the PM community.

Maybe.