The ProFTPD memcache support with the modules mod_memcache and mod_tls_memcache was droped because it requires dev-libs/libmemcached >= 0.41 which is not in the portage tree yet. As soon as a new version of dev-libs/libmemcached will be added to the portage tree I will readd the ProFTPD memcache support. See Gentoo Bug #354261 for more information about the dev-libs/libmemcached version bump.
A few days ago dev-libs/libmemcached-0.50 was added to the portage tree. But because of the ProFTPD Bug #3691 [1] I will wait to the next ProFTPD 1.3.4* release before readding memcache support to the ProFTPD ebuild. [1] http://bugs.proftpd.org/show_bug.cgi?id=3691
Fixed with 1.3.4rc3 bump, thanks Bernd