NOTE: Howard has since taken his site offline while he finds a suitable webhost, so the first link probably won't work
Howard Rogers recently touched on the knowledgeset (or lack thereof) of some interviewees with OCPs. We've all heard this before, and the common theme is that just because someone managed to pass the OCA and OCP exams, they still might not know nearly enough to be put in charge of your precious (and expensive) Oracle RDBMS. I've heard tale of people asking questions on oracle-l or the OTN forums like "What does ROWNUM mean?", while proclaiming their OCP title in their signature. So, yes, it is probably best not to just hire an OCP without verifying that they have the knowledge that you seek. "Trust, but verify" is an oft-used quote in the computing world, and it applies to hiring as well.
Now, as you may know, I am seeking the OCA/OCP certifications, after 5 years of learning on-the-job. I just completed the Oracle 10gR2 DBA Workshop I last week, which is a suggested course for the OCA exam, and I felt pretty comfortable with the majority of the material. It was nice to play with EM DB Control, which I don't (yet) have set up at my shop. Now I plan to go through the exam guide and review the course-provided books, then take the practice exam(s) provided with the exam guide. Then hopefully I'll be prepared to take that exam.
Why do I want the certification if so many gurus think it is practically worthless nowadays? Why not just be content in having the knowledge, without spending (or wasting, as they'd see it) time preparing for the exams? Probably for the same reason I finished school to get my bachelor's degree (which some people also say is watered down now): a sense of completion, mostly for myself. I don't expect the OCA or OCP to get me anything that I couldn't already achieve. However there may be a case down the road when having those certifications gets me a second look or a foot in the door with some non-technical HR staffer. One never knows how these things will fall out.