It's a pretty decent sized part of our blockchain history. People did it even when it was much much harder than twitter (cell phone and long waiting periods) ... i suppose it's a matter of the value desired and the cost associated.
There is not likely to be as much abuse NOW because the value of Hive is lower AND not many places are delegating as much SP/HP has steemit used to.
However regardless of how much HP is delegated for free there is value in the user-names and part of that value is lost potential in the hands of those who would have actually use them instead.
I think there is a solution in there somewhere and I'm trying to think through it... but also it doesn't matter how many our interfaces "onboard" it's how many quality users we bring in that stick around.
And we are agreed that I think a Custodial type account where new people sacrifice OWNERSHIP for EASE is a very viable option as long as they have a path toward actual ownership (which means non shared keys) and toward users that are responsible.