But most are using the same design and 30 or so domains at a time even in my small niche. It takes hours of work to find them all and then the filter is too full to add the next 50 or so that you find with the same layout and design a few days later.
Exactly that is the reason I had to remove Adsense from my holiday pages last shopping season - I couldn't keep up with the flood that kept coming in and replacing the ones I was putting on the filter daily. Same design, same account. Two, as a matter of fact. One was an email harvesting/lead generation operation offering FREE stuff with bogus offers (squeeze pages), the other was just best 5, best 6, best 10. That's the reason I hesitate to even bother with featuring any holidays any more, and probably won't until there's an option to filter by advertiser account, or deceptive "keywords" like FREE.
BTW, holiday or seasonal favorites - like decorations, wedding season,, etc. also cause inappropriate and wasteful specific ads running where they're completely irrelevant. Pages offering general, non-specific all-purpose widgets will bomb if ads are running specifically for wedding widgets. General "people's" apparel pages will bomb if ads are running for dog sweaters - and yes, I did once have that happening. And so do completely irrelevant, very specific widget ads run year-round, to the point where I'll have to take Adsense off the widget pages - which are VERY on topic for the "general" widgets and DO convert, based on a history of sales generated from affiliate links.
Pages that have good potential for converting for advertisers can get killed by inappropriate ad targeting - hence, we know our theme and target audience and should have better filtering capabilities. It would be better for us and definitely for advertisers (who make far more by acquiring new customers than we make for the click), and for the effectiveness of Google's program on the content network.