If you've got the building outline, adding addr:housenumber to it is great, but you can always just do a POI with that tag if not. You could do vacant block by having a POI with nothing else apart from the addr data.

I use the relation exclusively, since it means you don't have to add the street name to every single building (and makes it easier to fix if someone got the name wrong). If data conversion isn't using that and only uses addr:streetname, then we should probably fix the conversion to use it (regardless of whether people tag that way or not).

Sounds like it turned out well.

I don't know if it' spectacular enough to count as a Mapping Accident. Traffic was just slowing down a bit on the Riverside Expressway, and the guy behind me obviously didn't notice and crashed into the back of my car. Luckily there wasn't too much damage, it turned out to have broken the plastic part of the rear bumper, slightly dented the metal part, and pushed a mudguard up against a tyre slightly.

Hopefully I'll make it up that way whenever the next Sunshine Coast mapping party is :)