In April '07 we sent nearly 500 postcards out to our farm area, past clients and some friends, relatives & aquaintences. We used a reputable company that we have had good luck using before.
On April 23rd we got an email confirming the delivery to the post office for mailing. With a 4-5 day mailing time per the postal service the postcards were sure to arrive by April 30th.
It is now May 2nd and they still have not shown up.
The postcard company says they mailed them so they did their job.
The post office says they don't have them so they can't help me.
I tried looking up the number for the post office located in Nowhere but they must be unlisted! 
Anybody have any experience with this? What can we do? I'm just glad it wasn't 5000!
-Pete