Well in broad terms those also are getting paid up front or making you watch / listen to ads instead, sure. In the case of SEM, the industry puts kind of a lot

Well in broad terms those also are getting paid up front or making you watch / listen to ads instead, sure. In the case of SEM, the industry puts kind of a lot of energy into tracking ads, so it seems a little more straightforward to know how much I'm worth to them. But in more general terms, if we ever manage to sort out micropayments, I would prefer to pay as I go for everything - imagine the flat rate subscription model for say, your energy or water bill: "we're charging about what most families would use in a month; you say you're not a family of four? too bad."