I'm sure it would be fun to watch the competitors - the problem is that only few people would get involved and recorded the video of them singing. My estimation is that we would get 2, maybe 3 videos in 6 weeks.
I remember when I posted here a competition created by Endorphina game provider (http://www.kpvfaw.com/forum/competitions/good-chance-to-win-a-trip-to-crete-greece)
I found it on Instagram and instantly realised that anyone who joins the competition has extremely high chance of winning the great trip. The rules were simple:
"All you have to do is record yourself jumping with our Minotaurus and share your video on social media."
They had to extend the duration of the competition, because almost nobody actually joined.
When I look at the results now, you can actually see that only 3 people recorded the video during the whole competition duration, which which took almost 7 weeks. (https://www.instagram.com/explore/tags/jumptocrete/)
If anyone from this community recorded a nice video, I'm 100% sure they would win the trip to Crete.
This is a simple sign that's telling me that people aren't willing to record themselves or do anything more challenging.
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