It's a social network based on two promises:

1. It's beautiful, which they had to add because they knew just saying "we won't sell your data" would not go far enough. They needed that extra edge. In my humble opinion, it's actually quite ugly, so I find it pretty funny they are advertising this as a selling point.

2. They don't sell your data. We all know this is flawed because there is no promise this won't happen in the future, and to boot MOST normal people do not care about this.

Their initial launch had the right elements that allowed it to go viral and non-technical people started signing up. I would LOVE to see some stats from the Ello team around retention, as I am willing to bet a large sum of money that stat is really bad.