A couple of quick notes:
"Gangnam Style" is still getting airplay from some CHR stations, including Cumulus-owned B-100 Quad Cities
Most of the people posting a meme video of the "Harlem Shake" are over 18, and it's a big hit with the at-work office crowds.
Lastly, the CHR audience targets first and foremost 18-34 year old females, and they seem to be highly amused by the tune and its countless videos.
The record's popularity will likely fade pretty quickly, but there's nothing wrong with giving the "Harlem Shake" some exposure on CHR radio for the time being. We're not in the mid 90s when CHR radio was afraid to play novelty records like "Short Dick Man" by 20 Fingers, or "Cotton Eyed Joe" by Rednex.
Besides, I think part of the CHR audience is much more turned off by radio overplaying songs like "Thrift Shop" and "Don't You Worry Child" every hour. Meaning there's a possibility that part of your audience will tune into another station if they hear a song one too many times per day, just as they are when they hear an unfamiliar record that sounds different from the rest.
A good CHR will know how to navigate these waters, and find ways to continually excite their listeners, and keep them coming back for more.