My Bag has one pocket, and it's BIG. I like simplicity in my bags. I do not like complexity. My bag used to have a single inside flap, stitched to the top lip of the opening, with an assortment of little pockets for organizing stuff, but I removed it. It's not that I don't like being organized: it's just that I don't really like having someone else's principles of organization forced on me. The organizer pocket that was stitched inside this bag had a couple pen slots (I carry more than that and so I use a pencil case, which you can see in my profile picture), a wide pocket sized for something like a palm pilot (which most people now keep in a box in a closet, while they wait for the museum to call), a tinier fleece-lined pocket for a phone or media player (which is now a single device, and holstered to my strap for quick access while riding), and other miscellaneous slots that simply didn't fit the stuff I have. So out with the perma-pockets! The bag's a little lighter, it sits open more readily because there isn't a heavy array of pockets pulling the lip of the bag down, and is ready to be customized according to my needs.
Even when it left the factory - organizer pocket intact - my bag was downright simple compared to the modern daypack. Daypack design has gotten a little silly: the more specialized pockets, ports, sleeves, techy functions, fobs, and space age suspension technology a bag has, the more X-Treme you are, and the more money you will be separated from and ... the more doomed you are to throw away the bag as soon as your needs change. Think of it: you buy a new bag to fit your stuff. Your stuff breaks, or gets replaced with new stuff, or you stop using this stuff, or somebody invents a new piece of stuff that has an entirely different form-factor ... then you have pockets and features that are no longer relevant.
What if you don't have an MP3 player? Or you want to put it somewhere other than the specialized, padded media-pocket with a custom port for the headphones? What if you buy a bag with a padded pocket for your 12-inch laptop, then upgrade to a 15-inch? What if the water reservoir that came in the special insulated hydration-sleeve breaks or gets funky (it happens) and the new one you buy has the tube-thingy coming out of the wrong part and so doesn't reach out of the special hydro-hole and so on?
Custom pockets and padding and extra zippers add weight and more points of failure, and often stay empty for want of the Right Sized Thing. My bag, a Timbuk2 large Classic Messenger Bag (made in San Francisco), on the other hand, is insanely durable and beautifully flexible. In the one pocket of my bag, I have at different times carried a case of beer and snacks (ahem, to share), a full-size bike stand (a four foot long box ... it stuck out), camera bodies and multiple lenses, groceries, full picnics for a family of four on the beach or in the mountains (then all the rocks and stuff we collected to take home), and small ad hoc reference libraries. Basically, I can carry more in my bag than is wise, comfortable, or safe for anyone to carry while riding a bicycle. Of course when I only have a few things in it, it collapses to fit. It has no frame or foam suspension. It's a bag: it has the shape of the things it is carrying.
I do have the need to organize and carry small things: bike tools, pump, lights for night riding, food, extra clothes, books, journal, pencils and pens, and various other possibles. I have cheap little ditty bags and stuff sacks for all the things I carry, each one perfectly suited to my purposes because I chose it. If my needs change, I swap out the cheap bags. I put my laptop in a neoprene 'sleeve' that fits it like a glove. If I were to buy a bigger laptop, I'd get a different sleeve to fit it. What happens if the sleeve is stitched into the bag? And for that matter, what does the pocket do when you leave your laptop at home? What else do you put in a permanent, rectangular, foam-padded pocket? A very carefully folded sweater?
Bags with tons of pockets are also a serious liability in the rain. Bags with a lot of pockets and openings either have to use waterproof zippers and specially sealed seams (every stitch point is a point of entry for water in a downpour) or must be under a waterproof cover. My bag has one large, vinyl-coated, rain-proof flap, with no zippers to fail. Simple, beautiful, and durable.
(One extra provision I make for the possibility of really bad weather is the stuff sack that holds my rain gear: this bright orange bag is also waterproof. If the weather turns bad, the rain gear comes out and anything really sensitive to moisture goes inside the bag as extra insurance against water finding its way in.)
(low) tech writer principles. Rigid compartmentalization and design complexity limit flexibility and shorten the lifespan of a thing: complexity wears out its welcome sooner than simplicity. Complex things slow you down, require more maintenance (of a more specialized kind), solve problems you probably don't have, and cost more in the bargain.
Simplicity in design is more enduringly functional, flexible, adaptable, durable, and inexpensive (both on the day you buy it and when you need to repair it).