Over at Photography Stack Exchange, we have a biweekly photo submission contest on our main site. For awhile, the contest was just posted as a regular question, and in order to counteract the reputation boost I was receiving, I regularly gave away several bounties on the photo submissions. The presence of the photo contest on our main site definitely boosted our viewership, and we had lots of photo submissions, and the photo contests regularly hit HNQ, thus boosting participation.
But in an attempt to address some of the concerns about voting, "unearned" reputation boost, and the idea that our Photo of the Week contest questions were basically the glaring exception to what is usually considered a good question, I started making the PotW questions CW.
After making the PotW question CW, it seems the contests never make HNQ. Is that just a coincidence, or is it a consequence of marking those questions as CW?