"_" vs "-"

[Vadim Strizhevsky <vadim optonline net>]

This is probably a dumb question, but I haven't filled my quota today
yet:)

Is there some sinister meaning between choosing "_" or "-" as word separators 
in file names. I see both used in semi-consistent way and I get
confused. Is there some reason of having "email_conduit.c" and
"email-conduit-control-applet.c", instead of both having just "-" or
"_". Or is it just a matter of whatever you happened to name the file
first, and it stayed that way? Just curious. 

Another question, are the files "conduits/*/*-properties.c" just
obsolete remainders from earlier capplet versions and will be removed,
or are they used somehow and I can't see how?

-Vadim