Besides bringing some fun at the end of the year, some hat awards are meant to incite good behavior and also serve as more relaxed introduction to the Stack Exchange sites and their policies. While reading Tour or Help center is often ignored, reading hat description and their triggers is something more people will do and many will try to earn as many hats as they can.
In doing that it is important that required actions don't cause negative effects on the site or if they do encourage some easy to do action that can be applied recklessly, they do that in minimal possible manner.
For instance, in previous years there was a "Warm Welcome" hat where trigger was upvoting question posted by new contributor. People trying to get that hat without focusing on anything else, would upvote just about any question regardless of its quality. Since the requirement was upvoting just one question, the potential harm was not significant and the effects could have been easily mitigated by curators.
However, this year's Winter Bash, introduced not one, but three hats "Gem Detector", "Gem Finder" and "Gem Watcher" that require upvoting recent questions and require a lot more upvotes for the trigger - up to 50. Yes, there is additional constraint that such question needs to stay open, but that will not prevent people from upvoting anything counting just on luck and number of votes cast.
This kind of triggers are extremely disruptive for some sites, namely Stack Overflow, where there is not enough curators to deal with all poor questions. We cannot close all such questions, and inevitably, many of poor questions will now require additional curating and many will stay on the site, instead of being eventually deleted by roomba.
It is too late to change that for this year, but please in the future, when deciding on the triggers, don't just think about how the hat can be earned by people that will follow all other established rules, but also how can trigger be abused and how much disruption it can bring to the sites.
