I think they would be a lot more useful if they had little flags hanging
above them, giving an indication of which people might be interested in
them. For instance, not many Londoners would be interested in a plaque about
how the founder of Bolivia once lived in this house, whereas Bolivian
tourists would probably like to have it drawn to their attention that of all
the blue plaques in London, this is the one which is of interest to them, so
a little flagpole with a Bolivian flag above the blue plaque would help
everyone. I don't think it would spoil conservation areas either.