[db-wg] restrict usage of RIPE-NCC-RPSL-MNT

Dear working group,

The RIPE databse provides a mntner object which can be used to create
route objects for IP ranges which are not allocated or assigned through
the RIPE NCC.

http://www.ripe.net/data-tools/db/faq/faq-db/how-to-create-a-route-object-when-the-matching-ip-range-is-not-allocated-or-assigned-from-the-ripe-ncc

I did some digging to understand how the RIPE-NCC-RPSL-MNT mntner object
is used in practise. You can fetch the dataset through this command:
    
    $ whois -h whois.ripe.net -- '-K -i mnt-by RIPE-NCC-RPSL-MNT'

Usage exceeded my expectations:

    (object type: occurances)

    route: 12195
    route6: 77

And much to my suprise I found that there are all kinds of objects which
reference RIPE-NCC-RPSL-MNT with an "mnt-by:" attribute:

    aut-num: 341
    mntner: 51
    as-set: 37
    person: 40
    route-set: 33
    organisation: 5
    rtr-set: 1
    inet-rtr: 1
    key-cert: 1

Would it be an idea to prevent objects from being updated/created when
they carry a "mnt-by: RIPE-NCC-RPSL-MNT" attribute? 

Secondly, should RIPE NCC proactively remove all "mnt-by:
RIPE-NCC-RPSL-MNT" references from the database? 

Kind regards,

Job