> Due to the close proximity of the boxes 
> holding the bees, Drifting...

Sure, drifting can happen, but one has the same 
problem with hives on pallets, don't they?  My Dad 
is a big fan of brightly-painted plastic coffee-can 
lids thumb-tacked to the front of hives, and he 
keeps his hives in a very tight semi-circular line
year-round.

> and robbing may occur.

When the blooms are over, the hives go back to their 
yards and are  taken off the trailers.  Hives working 
blooms rarely get to robbing.

> colony manipulation becomes impossible without 
> major disruption.

Such a major disruption, sometimes I even 
get stung!  :)  Seriously, life is too short 
to work nasty bees.  I'd requeen if this 
became an issue.

> Disease transfer can occur with greater ease.

For some diseases, that's partly a function 
of drift, but for other diseases, drift is 
a very minor component, isn't it?

> Colonies are often in a heightened defensive 
> mode - where normal colony "investigation" can 
> lead to swirling mass of stinging bees.

Wow, got any video?  I've not seen or experienced 
this myself, nor has anyone every mentioned it to
me, despite bees being crammed into very close 
quarters by many backyard beekeepers who keep 
making splits.  I'd be willing to wager that
the overwhelming majority of beekeepers in 
North America keep their hives no more than
an arms length away from each other year round.

Here's what appears to be the earliest apiary ever 
found, and the hives were no more than a few inches 
apart, just about as close as one can get them on
a trailer.  

http://www.msnbc.msn.com/id/20588417/

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