Personally i really dislike the idea of any kind of private add-ons.
I would rather see all add-ons released, maybe not immediately, but at some point.
To me, the difference between personal and private add-ons is just minimal, the personal add-ons being pretty much private add-ons anyway.
I do get however that personal add-ons may attract more attention to a single server, but why keep it private/personal afterwards?
I am pretty sure some servers that used personal add-ons are not hosted anymore.
Why let that personal add-on get lost?
Overall, it's a bit of a grey area around private add-ons.