I think there are more possible options -- for instance, my personal preference would be to prohibit external search engine and site-wide searches of my content, but permit searches of my specific content -- e.g. people could come and search my posts on snails, or whatever, but if they searched Google or DW-as-a-whole for posts on snails, mine would not come up.

Which mostly has to do with me feeling like this is my social life, and that therefore I'm under no particular obligations to the internet as a whole to make it universally searchable.