gpmgroup - 6:31 pm on May 17, 2012 (gmt 0)
I've seen it used on a couple of utility sites. I can't see it being used too often though for a number of reasons.
1) Expressing Lat's and Long's isn't straightforward (degrees, mins, seconds / decimals etc.) never mind calculating them from Eastings and Northings and the various mapping projections etc.
2) On a server by server basis verification / quality assurance would be quite hard.
3) On a block basis the info is kind of there already at a country / region level of granularity and also much more likely to be third party verified. (Though of course sometimes it can be very wrong for individual servers within an address block.)