You've blown me away with this fabulous module. Congratulations on an excellent, well thought out implementation.
I'd like to see more calls to db_rewrite_sql(). I found I needed to modify a few of the queries for a multi-site implementation. Specifically, lines 50, 69 & 85 of adserve.inc, but it's probably a good idea to use db_rewrite_sql() everywhere. What do you think?