Well, we've been using this in the database world for quite a while (before you were born Alex!). Yah, there's lots of interesting stuff you can do with dynamic management of trees, and its nice to see it migrating to file systems now. Note that in the olden days, you wouldn't do this stuff because of the intense overhead (both processor and I/O) that was involved unless there was a big payoff (as there is with databases) although you'd usually do it over the weekend as a batch job.
With all this extra horsepower and disk space, heck, who cares!
Great note Alex!
Cheers,
Buffy