yeah, it wouldn't make much sense for shared hosting since to make really good use of memcached you would need at least 100MB RAM pre-allocated, although that number's entirely dependent on the size of your site, which is why bigger implementations are suited for more flexible hosting plans, etc. - it manages it fine however, so <3.
and also, thats a good point although memcached supports unix sockets since 1.2.4 accompanied by a `-s` arg to restrict a daemon to be accessed only by the current local user and not be exposed via networking etc. so that problem's p. much solved.