It's partly entropy-related wetware failure, but I'd be in trouble even if I were immortal. I have two many search-spaces and information stores in too many places.
Things aren't so bad in my personal domain - I have two search spaces. My Simplenote files (via NvAlt), Email (Mail.app) and Google Docs (via Google Drive and CloudPull ) are mirrored back to my Spotlight search space, and I use a Google custom search engine against my blogs, archived web site and app.net streams. So my two personal search spaces are private/secure and public. I can manage that , and I'm careful not to add anything that would require a third search space.
In my work domain though it's a mess. I have information scattered across several Wikis, multiple document stores, my local file system and multi-GB email store, and the remnants of blog whose server died. All of this in an environment that, for multiple reasons, is driving to an information half-life of 1 year. I have too many search spaces; I can no longer track them all.
So I'm launching Project Memfail :-). I need to rescope my search spaces - esp. my corporate one.
- fn -
 My main information loss over the past decade was GR Shares, I have some recovery there via CloudPull.
 Native spotlight search has issues, but I can work around those. Of course when Google Custom Search dies I'll be in for a painful transition.