Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 153; Flight Crew Type 20500
Situational Awareness; Time Pressure
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
General None Reported / Taken
Airport; Human Factors
Flight pushed 19 minutes late due to being weight restricted (take-off weight) and having to leave six passengers.  The Agent was doing a great job; but was very task saturated. The original load sheet came down with 167 passengers and 600 pounds under ATOG.  FAs counted passenger count five times; and each time came up with 169.  The Agent finally determined that we actually had 169; so new load sheet was created to reflect 169 Passengers. We were now at 200 pounds under ATOG. [We] calculated that our only take-off option was Runway XX; bleeds off; and flaps 25. This gave us a 268 FT stopping margin. We had NO MEL ITEMS.  Just prior to departure; it started to lightly sprinkle. Although the runway was still DRY; we quickly ran the calculations for WET-GOOD.  Takeoff was still allowable; but the stopping margin would have been 94 FT.  Takeoff was normal. In our climb; and still below 10;000 FT; a message popped up on ACARS.  We waited until climbing out of 10;000 FT to check it. That message was soon followed by a second identical message from Dispatch.  The message stated; 'OPS CALLED AND SAID TO ADD AN ADDITIONAL 10 BAGS IN BIN C'.  We did not respond to the message.  On a 737-800; any change requires a new load sheet. We had just taken off slightly over ATOG; and potentially out of balance.  We were well below Max Gross Weight and were not landing limited. The problem was with takeoff; and we had been airborne five minutes before the first Dispatch message. We continued the flight normally.It was late at night; unhappy passengers were being told they couldn't go.  The Agent was giving 110 percent and was under pressure to minimize the delay.  I'd be surprised to find this not to be somewhat common for this flight. Too many people; too much weight; too short runways; too long a [flight] distance. Nine out of ten times; it probably all works out.  This time it didn't.
B737-800 Captain reported taking off slightly over ATOG when the departure was rushed.