Sigmoid might make sense, although I don't know how popular a solution it would be. I figure anything that caps post value, effectively, would be frowned upon by a large segment of the steemit population - but at the same time, that sort of "regulation" might also help stabilize the platform for mass appeal.
This might all be a spit in the wind as ned has just recently dismissed non-linear reward curves in a comment on dan's recent post - and seemed to think quite highly of linear rewards.
Exactly because a sigmoid curve probably won't be accepted, and also because @ned favors a linear 'curve', I made my suggestion to combine n^2 with a linear function!
Right - but it seems like ned doesn't think things need to be changed at all - which seems contrary to a long term picture for the platform if mass adoption is actually a goal - but that's where it's at atm by the looks of it.
Having said that, the way you describe it, the n^2 into linear curve sounds appealing - I'm just not sure there is top down interest in changing the curve, period.