Re:We need a tag based filesystem (Score 1)

That's why you probably want to manage your tags in a hierarchy, and apply them to your files as you please. This would put birthdays under celebrations, and ex under people I know. This would probably fix most of the problems you refer to, but leaves you with a daunting task of defining your tag hierarchy. You'd also want auto completion of your tags in your application, so you don't have to cope with spelling errors and plurals and stuff. I am not advocating tagging or fixed hierarchies, but I think this would fix (or at least centralizes) most of your examples.