I just dropped into article 408 looking for 408.34 and it is no where to be seen. Interesting, I tried to find anything like it in 100, 220, or 225, but until I get my electronic version I am giving up.

Anyone know the reasoning or where it may be?

408.34 and 408.35 have both been deleted in the 2008 NEC.

The original reason that the 42 circuit maximum was written back in the 1930's was to prevent the rubber insulated conductors from being damaged by overcrowding and/or overheating. This is no longer an issue, so the 42 circuit limit is now history.

YIPEEE!!

I was looking for it for the lighting and appliance branch circuit panelboard for the tie in to 408.36 which has been totally rewritten also.

The number of disconnects on my main feeder to a building will total 4 one of which is a 15 amp, 240 VAC dosing station. The main feeder is protected remotely by a single breaker properly sized and even though the job is in California, it's a Federal project that will be built under the 2008. It was OK before, with some exceptions (like a feeder protected higher than the rating of the panel), but I wanted to be sure under the new. See 225.33 and NEC 2005 408.36(A) ex 1 versus 2008 408.36 (exception not required).

Please remember that just because the 42 circuit restriction has been removed it does not allow you to fill a panel with tandem breakers.
Only if the panel is listed for tandem breakers can you use them.

I agree. In this case here a 42 circuit panel would serve the building, but trying to be considerate to the electrician in getting runs through the stud walls, I am calling out 2 subpanels. It also helps to minimize penetrations through a firewall.