When Is Persistence Too .....Persistent?

Congratulations!  Your book is published.  Now you can relax, sit back, and wait for the royalty checks.  Right?  Wrong!  Unless you're REALLY well known, chances are your publisher expects you to do most, if not all, of your marketing.  So, if you want those all important book reviews, radio or TV interviews, or personal appearance/book signing opportunites, it's strictly "do it yourself."  Communicating with the right people to bring these opportunities about is critical, as is your manner of inquiry.  You research the guidelines and contacts, make your call or written request and wait.  And wait, and wait, and wait.  After an appropriate time of not receiving a response, you follow-up.  You craft a respectful message, acknowledging that you know this is a busy person, but you believe you have something their audience wants, and wait again.  Still no answer.  Remember, these are people who say on their websites that they want to hear from you!  Their voicemails always say that although they are not available at the moment, they will call you back as soon as possible.  But they don't.  Do you try a third time?  Do you just show up at their place of business (if geographically possible) where they can't avoid you?  I did it twice and it resulted in apologies for not returning my phone call or e-mail, and my obtaining two speaking engagements.  This can be tricky and probably the exception. I'd much prefer to have my initial query responded to.  Other authors have experienced this problem also.  I wish I had an answer.  Do you?  Any thoughts or experiences on how to circumvent being "ignored" would be welcome.