For a long time my whole life was in a textfile called 'phone numbers.txt'. It had started as a list of phone numbers of my friends (I didn't have a cell phone myself; dumb phones existed but I didn't want one) and grew into a huge repository of information.
For a while now I've been using pieces of paper which I file in numerus currens style and keep inside shoeboxes. Many tend to be thicker "fiche de la police"-type cardboard so the whole thing stays up even if there are also many loose folded-in-half A4 sheets. OTOH I've almost lost notes in the laundry and still rescued them with the hair dryer.
It's also hard to represent equations and diagrams in most note-takers. Interfaces, as the etymology suggests, really get in your way! The one drawback is to find oneself occasionally without paper. But again in a pinch even business cards and receipts (you can photocopy the termal paper at home later) are possible hacks.
(Numerus currens is like paper nosql: when you file a new note, first you quickly browse through your archives for similar topics, otherwise you number it max_N+1. If there's something similar with number 110, you might number 110/A, 110/B, 110/C; if something that belongs with 110/B comes, it's filed as 110/B/1... but you can never shake the whole thing out and lose the order, so I wouldn't recommend this system to people with large dogs or small children.)
