Default skeleton / directory structure

[freaky@]

Hey there,

I was just wondering, in the skeleton structure I only have 4 folders:
httpdocs
httpsdocs
error_docs
cgi-bin

Which is fine for us, however, new accounts, when they logon through ftp (and on shell access as well) see much much more, most of which we don't need (nor want):

anon_ftp
bin
cgi-bin
conf
error_docs
httpdocs
httpsdocs
pd
private
statistics
subdomains
web_users

Are these all required? Can I get rid of them and what creates them? A lot of them aren't in the skeleton...