I cringe every time I hear about a creative brief with "Viral" in the title. "Viral video", "viral social program" or "Viral Facebook app".
Advertisers don't make things "viral". People do. It's only when people discover something so funny, sexy, weird-ass, or ingenious that they're compelled to share it like mad and as a result, it becomes viral.
The best advertisers can do is create something that's probably out of their comfort zone and hope it will become a sharing phenomenon.
Here are couple of things that are keeping folks up at night and interrupting their work day. (Click on each caption to learn more).
Notice that there's only 1 advertiser.