adjacent parcels with shared ownership

gistfile1.sql

-- if you want to add a buffer, only do so around
-- one geometry, so you can still take advantage
-- of indexes
SELECT DISTINCT a.* from 
taxlots a
JOIN taxlots b
ON (a.owner1 in (b.owner1, b.owner2, b.owner3)
OR a.owner2 in (b.owner1, b.owner2, b.owner3)
OR a.owner3 in (b.owner1, b.owner2, b.owner3)
)
WHERE a.tlid<>b.tlid -- don't join to ourselves (which will always be true, and we'd just return the whole table)
AND st_intersects(a.the_geom,b.the_geom);