The lurkers aspect is not that serious. Every list has some.
But having over 1,500 lurkers is a concern for sure. The server has limited resources in terms of bandwidth. Imagine if the admins were to allow a post with a 1MB attachment. That is how much bandwidth used for 'readers' who are unlikely to collaborate again? Mailing lists are meant for collaboration. When lurkers outnumber the real collaborators, I kinda find it odd.
But it's okay!
Trolls/bullies are the easiest to take care of so I don't mind that. However, how do you get diversity from 'silent contributors'??
I am not being rigid. Actually, I stored the whole list of subscribers before I unsubscribed everyone so it's trivial to return it to that status it was in before, but given how long skunkworks has been in existence, I just thought maybe it makes sense to reconstitute. And such re-constitutions do happen ..
PS: Gicheru - point noted. As a matter of fact, I have myself added a few lurkers who are around to sniff for opportunities like you offered.