[Tagging] "contact:phone" or "phone" to combine with "amenity=telephone"

[Pieren]

http://wiki.openstreetmap.org/wiki/Tag:amenity%3Dtelephone
is saying that the phone box number has to be tagged with "contact:phone".

The "contact:" namespace has been discussed here
(http://lists.openstreetmap.org/pipermail/tagging/2011-May/007631.html)
and some good arguments have been raised against it.
Unfortunatelly, nothing really happend excepted some minor remarks and
the namespace is spreading in the wiki like in "amenity=telephone"
page but not in the database where it is only combined with "phone"
(http://taginfo.openstreetmap.org/tags/?key=amenity&value=telephone#combinations),
not "contact:phone".

I'm asking because the question why we don't use "phone" instead of
"contact:phone" is now asked on one of the translated version
(http://wiki.openstreetmap.org/wiki/FR_talk:Tag:amenity%3Dtelephone).

Can we use the taginfo stats to revert the change made the 2nd may
2010 where "phone" has been replaced by "contact:phone" and add a big
"deprecate" notice on the "contact:" namespace wiki ? (overall, we
still have 10 times more "phone" than "contact:phone", 20 times more
"website" than "contact:website", etc)

Pieren