Did I just not hear about this?
Once upon a time (Access97), if you compacted a table that had an autonumber field and if you had deleted records with the highest used autonumbers, the compacted table had its autonumber seed set to the last used autonumber. So for example, if you had 2500 autonumbers (1-2500) and deleted autonumbers 2001-2500 and then compacted, the next autonumber to be assigned would be #2001.
Apparently in Access2000 and 2003 this is no longer the case. Compacting does not affect the autonumber seed value. The only exception appears to be if the table is completely empty; then it works as before.
Seeing as how it took me this long to discover this, it obviously isn't a big deal to me. I'm just worried about what else I didn't hear about!