This Boing Boing post contains a reference to likely the most popular error made about intellectual property and digital rights management (DRM): that DRM "(adds) restriction on what can be done with something (people have) paid for." A purchase is a two way transaction, between a purchaser and a seller. Both have terms that define the transaction. For example, in the case of media such as CD's and DVD's, the seller's terms are clearly laid out on the packaging: no unauthorized copies are to be made, which in practice means no copies, because none are authorized by the seller.
DRM actually only applies to materials sold in purely digital form (hence the name) and to which DRM has been attached. By definition, DRM can't hamper one's right to "do something" with what he's "purchased," because the DRMed product is specifically what was sold. Implicit in this sale (and, I'm sure, laid out clearly in the sales agreement with whatever online store sold the material) is the idea that the DRM will remain in place and will dictate the product's use. The purchasers right, if he doesn't like those terms, is to simply not purchase the product.
Only if one asserts that a sale is an open-ended transaction for the purchaser, with no rights allowed to the seller and with the right to do anything he wants allowed to the purchaser, can one make the claim that DRM somehow stops the purchaser from using a product appropriately. Instead, DRM actually defines quite cleary what the purchaser is buying: that is, a digital product with certain inherent restrictions.
The fact that DRM is circumvented does not mitigate its appropriateness. Many people know how to circumvent automobile security, but there are no calls claiming that the inability to protect an automobile from theft means that it should no longer be subject to protection. Rather, automobile manufacturers continue to develop new and better ways to protect them.
The same should be done with intellectual property. Some sellers have given up on DRM, and are selling unprotected materials. That's their right, of course. It's a great evil, however, that they do so primarily because they see no other choice.