I used to work in sponsored research into new drug entities. There are a couple other reasons that placebo may be becoming more effective, which is a clever way of saying new drugs are less effective.
First, developing a new drug is a very high-risk undertaking. Even if you don't buy the oft-cited US$800million figure for developing a new drug, it's still a tough sell to the MBA's who manage R&D and production operations. None of these managers wants to lose their jobs for missing quarterly numbers, so even though it often takes several years to recognize return on R&D investment, there is little incentive to strike out into something completely new. A number of new drugs I have seen are merely tweaks of existing compounds (e.g. Lexapro) that promise only marginal improvement over the existing compound (Celexa), but extend patent protection over the brand name. Truly novel compounds are being developed, but lately these are very specialized compounds in "hot" fields like cancer.
Speaking of cancer drug development, another reason that placebo effect may seem stronger is that the patients who might benefit the most may be excluded from trials for liability reasons. The Vioxx lawsuit has spooked everyone in the field. When a new compound shows even the possibility of cardiac side effects, it won't even be offered to patients with cardiac complications. It's becoming safer to let them die naturally of leukemia than offer them a novel treament that might risk scuttling a study and possibly an entire project because of a small possiblity of side effects that could expose the sponsoring company to a lawsuit.