I've just gone through the first page of [tag:code-challenge]. Out of 15 puzzles, 5 are also tagged [tag:code-golf]; two have other objective or intended-to-be objective winning criteria (respectively ratio of output to input; and algorithmic complexity); three have subjective winning criteria; and five have no winning criteria at all.

All five of those which have no winning criteria, and two of the three with subjective criteria, date from the early days of the site (no later than March). The only recent question which has a subjective criterion is [Creative Programming](http://codegolf.stackexchange.com/questions/3245/creative-programming); I would say that it's a case where [We need more discipline and down-votes](https://codegolf.meta.stackexchange.com/questions/397/we-need-more-discipline-and-downvotes) applies.