To be most useful, YNAB should know my passive spending, and then harass me about all the dollars I am not reporting. Otherwise, I can just leak money and not talk about it.
I fully agree. It seems a little silly that if you have a busy period at work and forget to pay attention for a few weeks, that's just a black hole (short of going through credit card statements and trying to remember every cash purchase). This happens all the time with Mint, and I can just go back and categorize all the purchases that need doing so, with the only loss being that the cash purchases I forgot about show up as non-specific cash spending (through the initial ATM withdrawal).