Is it a good idea to doorknock other physician offices for clinical trial patient referrals?

It is no mystery that patient recruitment is the single biggest barrier to the success of most clinical trials.  One possible method for improving recruitment at the research site level is perhaps door knocking other medical practices and physician offices in order to get patient referrals from them.  As most things go, this is far easier said than done, and it is my personal belief that most sites simply do not do enough if any door knocking of their own for a multitude of reasons that would probably make for an excellent follow up blog post.