Kristina writes...
This has been informally nicknamed a "mite bomb,"
and, though not studied extensively, seems to be commonplace in
urban/suburban novice beekeeping situations.

my comments..
Well just to be totally up front here Kristina this sounds like an urban legend both in it's origin and it's telling.  Do we have any real evidence that such an event really exist?   Finally over the years you (I) see the trend when the current buggy man is blamed for every death of every hive no matter where it happens or how it happens and it seems like the current 'cause' to point to is varroa.  This is not to say varroa is not a concern and several here have pointed to exactly what I look for in a dead out.... that is 1) debris on the bottom board and 2) varroa scat around the last existing brood area.  This does give me some pretty good idea of the degree of varroa infestation in that hives but it does not necessarily translate into varroa being the cause of the hives decline.  I think it is getting to be much better understood that the disease and virus that varroa carries with it may actually be more detrimental to the honeybee than varroa itself.

And finally no matter what is your preferred method of monitoring for varroa ALL the processes are fraught with a large error term which can only be reduced by practice.  For the true hobby beekeeper who ones one or two hives this obviously could be a large issue.  

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