i would propose a better question (for which I couldn't find answer yet - although I've read somewhere, that this matter has been discussed many times already):

Why isn't the root filesystem only used for very basic system stuff (kernel + some failsafe system, which would at least provide busybox, if something went terribly wrong)? And the rest of it - /usr, /var, /home could then be on separate partition (e.g. 4GB), which would be mounted asap during boot...

That way, no /opt-ifying crap would be needed and one would hardly hit no-disk-space error...

Only using / for basic system (could fit even into a 64MB partition, easily), and /usr for all the other stuff is quite standard way to do things on "desktop linux" - and it's very scalable too...

Is there any relevant discussion in this forum - or did the discussion only take place in Nokia (or at maemo summit)?