This boils down to the whole SaaS (Software as a Service) model vs. traditional software models. Do you want to pay the recurring small subscription payments, but lose access if you cancel your sub, or do you want to pay much more up front for permanent access? In the software business, this debate has been going on for several years. Which is better for a given consumer varies a lot depending on the particulars of the software (initial cost, frequency of updates, etc.) and the needs of the consumer (will they need upgrades, how many copies, etc.)
MS did offer a version of Office as a subscription (MS Equipt). It is $70 for one year for three computers, including their anti-virus and anti-spyware stuff. $70 sounds pretty good considering the full version of office of that edition is $250-300 for a single copy. With a new version of Office coming out every 3-4 years, if you have multiple computers and plan to upgrade to the new versions as they are released the subscription model puts you way ahead cost-wise. If you have a single computer and only upgrade office every couple of versions, you are probably better off just buying it outright.
For the CB, would you be willing to pay $40-50 for the initial program, then pay for repeatedly for upgrades to add new material to it? If you want all the latest material as it is released, the SaaS model is probably a lot less expensive, both in the short run and in the long run as long as updated content is coming out. If you don't care about the new material and don't mind it being core, or core plus a few select upgrades, an outright purchase model would probably be better.
Paying for access to the CB doesn't bother me any more than I was bothered that I could no longer search or set a custom title when my EN World CS sub ran out. I look at DDI as primarily paying for the electronic magazines (buying equivalent content each month at RPG Now would probably cost at least the same as the DDI sub), and the CB, Compendium, and the rest are just a bonus.
