I don't personally see a reason for plural locations, but it would be
nice if it recursed (that is, looked for .so's in subdirectories). My reason for this is that I work on applications which have in-house extensions as well as public ones, and I'd like to keep the two separated by directory.
I gave one example of a use-case for multiple directories upthread - the Postgres.app mac app has contrib, plv8 and postgis bundled under its application folder, but it would be nice to allow users to drop extra extensions under ~/Library/Postgres.app somewhere.
If we had directory recursion then you could sort of fake it using symlinks (as long as we follow the symlinks) but it's pretty messy, the wrapper app would have to make a dir under ~/Library the actual extension dir and have a symlink back to its bundled extensions. Not the end of the world though.
For any of that to work the dir (or dirs) would need to be settable by config or startup option - compiled in wouldn't cut it, since the absolute dir of the end user's home directory isn't known at compile time.
