It's not inherently bad for someone to merit announcement threads, since you might legitimately view them as particularly interesting and noteworthy.
That is something new... there are high chances people will start using merits as "likes"... if they like something they will give merit to it. Specially announcements and bounties are mostly sugar coated, nicely formatted and attractively written posts and they will gets likes for sure so you won't be able to find loopholes at first glance only later at stage truth gets revealed.
Also there should be a difference between announcement and bounty traps and merit sources should consider this.
Edit: Have the merit sources decreased recently?