It's a dream, a truly beautiful one, but it never works (does it? has anyone pulled it off?). Taking it to an extreme, the entire world needs one integrated dat

It's a dream, a truly beautiful one, but it never works (does it? has anyone pulled it off?). Taking it to an extreme, the entire world needs one integrated database and user authorizations. Obviously data structures vary, performance is required, and it becomes a bottleneck because it's so critical that mortals can't touch it and every change must be ultra-safe. And then there's security: what if someone finds a way from the development bug section to the HR or executive-only financials sections? Generally, anyone who has tried to implement universal ERM systems knows how difficult and painful integrated systems can be. But those are the extremes. I'd be interested to know how far people have gotten, and how they did it, pursuing this ideal? I've never seen a business run on one. How about a personal knowledge-management system? Does everything fit? Do you still use spreadsheets for something 'quick', text files for free-form, etc.?