>and then probably get boring once the novelty wore off

You might need something to augment that novelty. Maybe instead of a blogging platform, some kind of PostSecret like app where people post anonymously with video backdrops instead of cards. This would be better than a blogging platform as well because it would encourage (or perhaps even limit) small blocks of text which would fit into a small space without needing a scrollbar.

But anonymously posting secrets in the form of videos with a small caption would make the videos look rather 'not like secrets'. I would rather prefer it as a microblogging platform than a secret sharing platform with video snippet captured while the text was being written, in the background...