Why does "???" replace some values in this p2pool output? 2013-07-09 00:46:43.467000 P2Pool: 17468 shares in chain (17472 verified/17472 total) Peers: 9 (3 incoming)
2013-07-09 00:46:43.467000  Local: 0H/s in last 0.0 seconds Local dead on arrival: ??? Expected time to share: ???
2013-07-09 00:46:43.468000  Shares: 0 (0 orphan, 0 dead) Stale rate: ??? Efficiency: ??? Current payout: 0.0000 BTC
2013-07-09 00:46:43.468000  Pool: 1202GH/s Stale rate: 16.9% Expected time to block: 21.2 hours


Why are a bunch of values just "???".
2013-07-09 00:46:43.467000  Local: 0H/s in last 0.0 seconds Local dead
  on arrival: ??? Expected time to share: ???


There is no miner attached to the pool, "0H/s" means zero hashes per second.  And since no hashing is being performed the dead on arrival and time to share cannot be calculated, and thus are unknown.


  2013-07-09 00:46:43.468000  Shares: 0 (0 orphan, 0 dead) Stale rate:
  ??? Efficiency: ??? Current payout: 0.0000 BTC


Since mining is not occurring, the stale rate and the efficiency cannot be calculated, and thus are unknown.

You need to attach a miner to the p2pool to actually mine BitCoins.  Try something like GUIMiner.