>>About a third of all the taxa that have ever been named are invalid
>>synonyms or homonyms. As shown in monographic revisions of genera and
>>families, this ratio remains remarkably constant through the years despite
>>changes in taxonomic philosophy,....

In properly executed (lots of work!!) monographs on groups that haven't
been examined for many moons, many (perhaps a third, I don't know) fall
into synonomy.  Let me qualify that.... at least in land snails....we don't
get monographs very often.  Then, however, based on newly available
material, the number of taxa bloom again, usually gaining well over the
number lost to synonomy.  This has happened time and again.

This has happened in every other discipline as well.  People are looking at
monitor lizards more carefully (not DNA stuff, just more carefully and more
material is available) now and finding unrecognized subspecies and more.
These are 1 to 6 foot (and bigger) long lizards, so it's not just the small
critters of the world.

For example, I bet you, dollars to doughnuts (will that translate for our
international constiuency?), that if/when the Neritidae is properly
monographed, names will be relegated to synonomy by the droves, but these
will be more than replaced by cryptic and unrecognized species as the
material is examined.

Who decides?  The person doing the looking.

Kurt